Remove get_segment_info and passing segment_info through globals
Fix bold attr that may leak into next segment
Some lint fixes

* Fixed handling of empty scalars in python2: ''.join([]) returns str,
  ''.join([u'smth']) returns unicode
* Fixed check_config: it was always checking for themes, even if it was
  requested to check colorscheme
Added support for all powerline prompts (in2, out, rewrite)

Also fixed problem with prompt not really updating.

Fixes #141