Merge remote-tracking branch 'origin/develop' into tuxdude-dev

Conflicts:
	powerline/config_files/colorschemes/tmux/default.json
	powerline/config_files/config.json
Fix the segments in powerline.segments.tuxy

The following segments should now work:
- spacer
- sandbox_flavor
- sandbox_id
- virtualenv

Also use the branch segment from common until the one in tuxy is fixed.
Propagate segment info from default->termsaber.
Propagate default->termsaber for ipython theme.
Renamed the description for termsaber colorscheme.
Enable status_colors with branch segment.
Support Perforce BRANCHNAME in branch segment.

Add support for checking and returning BRANCHNAME (i.e. a perforce repo
where the user has set the BRANCHNAME variable). The status is always
returned as dirty.