Updated all plugins that are non-forked. Added some new plugins.

Added update_plugins.py which can fetch new plugins from GitHub.

New plugins added: zencoding, vim-indent-object, taglist, nginx.vim

sources_non_forked/vim-powerline/autoload/Powerline/Segments/rvm.vim

@@ -1,6 +0,0 @@
-let g:Powerline#Segments#rvm#segments = Pl#Segment#Init(['rvm',
-	\ (exists('g:loaded_rvm') && g:loaded_rvm == 1),
-	\
-	\ Pl#Segment#Create('string', '%{rvm#string()}'),
-	\ Pl#Segment#Create('statusline', '%{rvm#statusline()}')
-\ ])