add mouse support toggle for vimrc, and re-enable NERDTree on arg-less start

Also, tidy up vimrc a bit, but moving functions to the bottom

vim/vimrc

@@ -32,9 +32,7 @@ if has("persistent_undo")
     set undodir=~/.vimundo
 endif
 
-" mouse support. TODO: Are there any checks we should be doing?
 set ttymouse=xterm2
-set mouse=a
 
 if has("autocmd")
     " Enable filetype specific features
@@ -70,9 +68,9 @@ endif
 function! StartUp()
     " Stuff in here will be called by autocmd below
     " example, start NERDTree if vim called with no arguments
-    "if 0 == argc()
-        "NERDTree
-    "end
+    if 0 == argc()
+        NERDTree
+    end
 endfunction
 
 
@@ -89,6 +87,7 @@ set softtabstop=2   " let backspace delete indent
 set wrap lbr        " wrap long lines of text
 set backspace=eol,start,indent "backspace over everything
 set textwidth=80
+set colorcolumn=+1  " mark out the limits of the textwidth
 
 
 """"""""
@@ -99,7 +98,6 @@ syntax enable
 colorscheme solarized
 set t_Co=16
 set background=dark
-set colorcolumn=+1
 hi Folded ctermfg=darkred "set colour for folded lines
 
 
@@ -120,20 +118,7 @@ set laststatus=2 "always show a status line
 
 set foldmethod=indent
 set foldlevel=10
-set foldtext=MyFoldText()
-
-function! MyFoldText()
-    let line = getline(v:foldstart)
-    let indent = indent(v:foldstart)
-    let indentOnly = strpart(line, 0, indent-1)
-    let linecount = v:foldend+1 - v:foldstart
-    let plural = ""
-    if linecount != 1
-        let plural = "s"
-    endif
-    let foldtext = '+'.indentOnly.'... ('.linecount.' More lines)'
-    return foldtext
-endfunction
+set foldtext=FoldText()
 
 
 """"""""
@@ -164,70 +149,37 @@ imap II <Esc>
 nmap <leader>j o<Esc>k
 nmap <leader>k O<Esc>j
 
-" Toggle numbering
 nmap <silent> <leader>n    :set number!<CR>
-" Toggle wrap
 nmap <silent> <leader>w    :set wrap!<CR>
-" Toggle paste with/without indenting
+
+" Toggle paste mode - no autoindenting of pasted material
 nmap <silent> <leader>p    :set paste! paste?<CR>
-" Toggle showing whitespace characters
-nmap <silent> <leader>l    :set list! <CR>
+
+" Toggle visible whitespace characters
+nmap <silent> <leader>l    :set list!<CR>
+
 " Toggle scrollbind for moving multiple splits in sync together
 nmap <silent> <leader>s    :set scrollbind! scrollbind?<CR>
+
+" Toggle mouse support.
+nnoremap <leader>m         :call ToggleMouse()<CR>
+
 " Toggle NERDTree instead of the normal dir browser... Doesn't seem to work yet
-nmap <silent> <leader>d    :NERDTreeToggle<CR>
+nnoremap <silent> <leader>d    :NERDTreeToggle<CR>
+
 " Toggle Commenting out lines with NERDCommenter
 nnoremap <silent> <leader>,    :call NERDComment("n", "toggle")<CR>
 vnoremap <silent> <leader>,    <ESC>:call NERDComment("x", "toggle")<CR>
 
-" Vim's Undo Tree with Gundo!
+" Traverse undo tree with Gundo!
 nnoremap <leader>u :GundoToggle<CR>
 
-" Search with ack!
+" Search under cursor with ack!
 nnoremap <leader>a :Ack <cword><CR>
 nnoremap <leader>A :Ack -a <cword><CR>
 vnoremap <leader>a :Ack <cword><CR>
 vnoremap <leader>A :Ack -a <cword><CR>
 
-" Colemak layout for INSERT mode only
-" Qwerty  - qwertyuiopasdfghjkl;'zxcvbnm,./
-" Colemak - qwfpgjluy;arstdhneio'zxcvbkm,./
-"inoremap <silent> e f
-"inoremap <silent> r p
-"inoremap <silent> t g
-"inoremap <silent> y j
-"inoremap <silent> u l
-"inoremap <silent> i u
-"inoremap <silent> o y
-"inoremap <silent> p ;
-"inoremap <silent> s r
-"inoremap <silent> d s
-"inoremap <silent> f t
-"inoremap <silent> g d
-"inoremap <silent> j n
-"inoremap <silent> k e
-"inoremap <silent> l i
-"inoremap <silent> ; o
-"inoremap <silent> n k
-
-"inoremap <silent> E F
-"inoremap <silent> R P
-"inoremap <silent> T G
-"inoremap <silent> Y J
-"inoremap <silent> U L
-"inoremap <silent> I U
-"inoremap <silent> O Y
-"inoremap <silent> P :
-"inoremap <silent> S R
-"inoremap <silent> D S
-"inoremap <silent> F T
-"inoremap <silent> G D
-"inoremap <silent> J N
-"inoremap <silent> K E
-"inoremap <silent> L I
-"inoremap <silent> : O
-"inoremap <silent> N K
-
 
 """"""""
 "" Key Remaps - Movement and Windows
@@ -237,21 +189,13 @@ vnoremap <leader>A :Ack -a <cword><CR>
 nmap H ^
 nmap L $
 
-" Smart way to move btw. windows
+" Smart way to move between windows
 nmap <C-j> <C-W>j
 nmap <C-k> <C-W>k
 nmap <C-h> <C-W>h
 nmap <C-l> <C-W>l
 
 " mapping to make movements operate on 1 screen line in wrap mode
-function! ScreenMovement(movement)
-    if &wrap
-        return "g" . a:movement
-    else
-        return a:movement
-    endif
-endfunction
-
 onoremap <silent> <expr> j ScreenMovement("j")
 onoremap <silent> <expr> k ScreenMovement("k")
 onoremap <silent> <expr> 0 ScreenMovement("0")
@@ -276,3 +220,79 @@ if s:uname == "Darwin"
 endif
 
 " let g:SuperTabDefaultCompletionType = 'context'
+
+
+""""""""
+"" Functions, the Givers of Power (in order of use)
+""""""""""""""""""""""""""""""""""""""""""""""""""""""""
+
+function! FoldText()
+    let line = getline(v:foldstart)
+    let indent = indent(v:foldstart)
+    let indentOnly = strpart(line, 0, indent-1)
+    let linecount = v:foldend+1 - v:foldstart
+    let plural = ""
+    if linecount != 1
+        let plural = "s"
+    endif
+    let foldtext = '+'.indentOnly.'... ('.linecount.' More lines)'
+    return foldtext
+endfunction
+
+function! ToggleMouse()
+  if &mouse == 'a'
+    set mouse=
+    echo "Mouse usage disabled"
+  else
+    set mouse=a
+    echo "Mouse usage enabled"
+  endif
+endfunction
+
+function! ScreenMovement(movement)
+    if &wrap
+        return "g" . a:movement
+    else
+        return a:movement
+    endif
+endfunction
+
+
+" Colemak layout for INSERT mode only
+" Qwerty  - qwertyuiopasdfghjkl;'zxcvbnm,./
+" Colemak - qwfpgjluy;arstdhneio'zxcvbkm,./
+"inoremap <silent> e f
+"inoremap <silent> r p
+"inoremap <silent> t g
+"inoremap <silent> y j
+"inoremap <silent> u l
+"inoremap <silent> i u
+"inoremap <silent> o y
+"inoremap <silent> p ;
+"inoremap <silent> s r
+"inoremap <silent> d s
+"inoremap <silent> f t
+"inoremap <silent> g d
+"inoremap <silent> j n
+"inoremap <silent> k e
+"inoremap <silent> l i
+"inoremap <silent> ; o
+"inoremap <silent> n k
+
+"inoremap <silent> E F
+"inoremap <silent> R P
+"inoremap <silent> T G
+"inoremap <silent> Y J
+"inoremap <silent> U L
+"inoremap <silent> I U
+"inoremap <silent> O Y
+"inoremap <silent> P :
+"inoremap <silent> S R
+"inoremap <silent> D S
+"inoremap <silent> F T
+"inoremap <silent> G D
+"inoremap <silent> J N
+"inoremap <silent> K E
+"inoremap <silent> L I
+"inoremap <silent> : O
+"inoremap <silent> N K