Snipmate description updated

Scrooloose snippets were replaced with honza/vim-snippets.
Snipmate's version notice removed

Another snipmate's fork (garbas/vim-snipmate) is used now. The notice is
obsolete now.
Merge pull request #465 from vdmgolub/snipmate_docs_update

Snipmate docs update
Update vim-improvements.vundle

This removes a redundant Bundle that already appears on line 9. This was throwing warnings for me whenever I started macvim.
Merge pull request #470 from martco/patch-1

Update vim-improvements.vundle
Decided disabling arrow keys was hurting new people too much
Remove duplicated plugin
Fix Ag functions

I believe this is what is intended? It was not working for me like it was...
Merge pull request #474 from lfilho/patch-1

Fix Ag functions
Remove tagbar settings [Fix #464]
Add vim command for updating current working directory
Add OSX keychain helper for git credentials
Include additional plugins
Switch to hybrid line numbering
Reduce VIM default window size
Make Google Chrome the default preview app
Add ability to upload git achievements to live gh-pages branch
Add Taskwarrior support
Update prezto
Modified prezto