Merge pull request #1 from dflock/master

Added two new segments
Fixing subprocess.check_output for old python

The `check_output` function was introduced in Python 2.7, so in order
to keep this running on older versions, the code from the 2.7
release is patched in here.
Fixed uptime segment for Windows with 24-hr clock
Adding monokai theme

Pulled from https://github.com/adambullmer/powerline-shell
Fixing bug in 12/24 hour processing for Windows uptime segment
Fixing backwards-compatibility patches

Several functions are patched in for compatibility with various
versions of Python. These patches are now done the same way.