Vim: Fix quick way to unset last search, instead of Enter it is now Esc

This was done so that the ack.vim plugin would respond to 'enter'
Vim: Fix auto-reload of vimrc upon saving it

Fix:
 * Vimrc auto-reload upon save

Add:
 * Comment regarding default shell
Vim: Add ability for vim to auto-rebalance windows upon resizing vim
Vim: Improve CtrlP/grep to use ag, adjut ctrlp match window size

Add:
 * Ability to use ag in grep and CtrlP
 * Explicit size for CtrlP match window
Vim: Add NERDTreeFind map <leader><f2> (quickly go to file in NERDTree)
Vim: Fix issue with <esc> as way to unset last search, now uses ;

For some reason using <esc> to unset the last search casued an issue
when vim started up (seems like it was in an deleting insert mode).