Add i3 bindings and segments
Use 'with' instead of lock.acquire/release()
Improved battery segment:

- Ignore `steps` if gamify is False.
- Add `full_heart` and `empty_heart` keywords.
- Document `format` keyword.
- Replace `draw_soft_divider` with `draw_inner_divider`.
Merge pull request #792 from ZyX-I/improved-battery

Improved battery segment:

Closes #791.
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
In fish also check for presence of powerline in $PATH
Check for TMUX only once, check whether $TMUX is writeable

Fixes #801
Disable mode support on <=zsh-4.3.10

Fixes #800
Some style fixes
Move i3bgbar.py to i3bar.py
Merge branch 'i3-fixes' into develop
Merge pull request #806 from ZyX-I/shell-fixes

Shell fixes: TMUX support for su[do] and modes on old zsh
Merge branch 'develop' into local-develop