Provide ability to revert back to the previous version of powerline
Add <leader>gw for :Gwrite in fugitive
Added the branch via bash variable to the git pull command when updating.
Update GitGutter after writing to the index.
Add GitGutter toggle similar to other git shortcuts.

All of the other shortcuts are related to fugitive, but I feel that it's best to
just put the "git-related" shortcuts together. <leader>gg shouldn't conflict
with any git commands other than grep, which probably much less frequently used.
cleanup