Add i3 bindings and segments
Use 'with' instead of lock.acquire/release()
Fix docstring for i3wm.workspaces segment
Remove dead code from renderers/i3bgbar.py
Adapt to python3 / __future__ print statement
Fix highlighting groups for workspaces segment
Update documentation to include i3 instructions
Merge pull request #782 from S0lll0s/feature/i3

Add i3 bindings, segments and renderer