Added RVM Segment to VIM

- Added RVM current segment to VIM.
- Updated colorschemes for rvm_current.
- Updated default config to include RVM string.
Fixed insert mode colors for rvm_current
Updated vim solorized colorscheme
Readding try catch to fail gracefully
Converted RVMSegment to a ThrededSegment

- As requested by @ZyX-I, Lokaltog/powerline#349, not polling in the
  main thread.
Updated RVMSegment

- Switched to using Popen like readlines.
- Added **kwargs to render method.
- Removed highlight group since it is not required when the group name
  is same as the function name.

Lokaltog/powerline#349
Added RbEnvSegment

- Renamed highlight groups as ruby_version and applied to both
  RvmSegment and RbEnvSegment. Currently switched theme to show
  ruby_version from rvm or rbenv.
Fixed RvmSegment & RbEnvSegment
Updated config for quickfix
[Fix] rvm_current segment
Updated RVMSegment & RbEnvSegment
Merge branch 'develop' of git://github.com/dhruvasagar/powerline into develop

Conflicts:
	powerline/segments/vim.py