Add syntax plugins for

* jinja
* less
* javascript/json
* coffee-script
* ansible
Use double esc to clear the last used search pattern
Don't remap : to ; in command mode

This may break some commands or abbreviations which use the expression
register:

cabbr ag <c-r>=(getcmdpos() == 1 ? 'Ag' : 'ag')<cr>
Define ag command to search text and open a quickfix list with matches

Command respects ag arguments and has abbreviation, that works only it's the
first word on command line.

Based on http://robots.thoughtbot.com/faster-grepping-in-vim.