updated documentation and comments for .vimrc.before
Merge pull request #435 from mikedfunk/vimrc_before

updated documentation and comments for .vimrc.before
before -> before.local & adding before.fork
Update README to reflect before changing to before.local & add of before.fork
Conditionally override airline separators only if powerline fonts are not used.

The Airline separators were unconditionally overridden. I have conditionally overridden the separators only if the user doesn't use Powerline fonts.

User is expected to specify `g:airline_powerline_fonts=1` in `~/.vimrc.before.local` instead of `~/.vimrc.local`.
Merge pull request #441 from SaswatPadhi/Fix-for-overridden-airline-separators

Conditionally override airline separators only if powerline fonts are not used
Populate .vimrc.before with all spf13 options

* .vimrc.before should not be modified (just like any other non-local
  or non-fork config file)
* .vimrc.before contains a list of all options that can be set
* .vimrc.before.local is where these options would actually be set
* support .vimrc.before and .vimrc.before.fork in install scripts
Option to clear instead of toggle search highlighting
Fix solarized if statement

endif came before setting all options
Update some formatting