Environment: add /usr/local/heroku/bin to PATH
Vim: show boundary of 100-column textwidth
Vim: rename 'Keyboard mapping' section to 'Mappings'
Vim: add mapping mode notes
Vim: use nnoremap for window navigation mappings
Vim: switch to last file with <leader><leader>
Vim: open splits below and vsplits to the right
Vim: alphabetize options (ignoring 'no' prefix)
Vim: prevent JS parsing warnings in :Rtags