Create Manhunt buffer instead of quickfix.
Add L/R signs to Manhunt window.
Change next/prev diff default mappings.

To match Vim's defaults.
Add pin mode.
Correct pin mode error message.
Update Vim help doc for v0.3.0.
Update Vim help doc again for v0.3.0.
Update README.md for v0.3.0.
Fix README.md formatting.
Fix ASCII drawings.