Merge branch 'develop'

Merge changes from the develop branch:
- many fixes, in particular for MacOS X (battery)
- many speed improvments (Mercurial, Subversion)
- many reliability improvments (SHORTEN_PATH feature)
Ready for a release.
Merge branch 'develop' of github.com:nojhan/liquidprompt into develop

* 'develop' of github.com:nojhan/liquidprompt:
Restore official _lp_hg_branch_color()
Restore LP_ENABLE_HG_OUTGOING macro.
BUG correct.
has_commit is an integer.