Powerline-shell

* New generic `stdout` and `env` segments

* Support for custom themes
* New option for the `time` segment to specify format of the displayed time
([dundalek](https://github.com/b-ryan/powerline-shell/pull/383))

* Reverted fix for
([249](https://github.com/b-ryan/powerline-shell/issues/249)) because it
caused issues on Mac.

* New theme! (gruvbox)
([monicaycli](https://github.com/b-ryan/powerline-shell/pull/388))

* Fix hostname colorize bug
([comagnaw](https://github.com/b-ryan/powerline-shell/issues/353))
* Fix issue with prompt bleeding behavior
([bytebeast](https://github.com/b-ryan/powerline-shell/issues/249))
* Better error message when config file cannot be decoded (Closes
[371](https://github.com/b-ryan/powerline-shell/issues/371))

* Fix Python 3 compatibility of `git_stash` segment