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 The notice is
obsolete now.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
Merge remote-tracking branch 'upstream/master'

* upstream/master:
  Decided disabling arrow keys was hurting new people too much
  Update vim-improvements.vundle
  Snipmate's version notice removed
  Snipmate description updated