Remove calls to Rnavcommand. Closes issue #12

Rnavcommand has been deprected. Instead of adding in settings for
rails-projections, I choose to leave it up to the individual to setup
their own projects in `.vimrc.local`.
Add some documentation to `tmux.conf.osx`
Merge remote-tracking branch 'thefishbowl/master'
Move custom vim settings to .vimrc.local