this was breaking on os x
Merge pull request #86 from emergion/master

Lusty Juggler crashing on OS X Vim 73
crashing vim 73 on os x, workaround for strange behaviour in vim and ruby
Merge pull request #87 from emergion/master

Lusty Juggler crashing on OS X Vim 73
Add some more cancel keys.

Any keys that would make vim enter insert/replace mode will break
LustyJuggler. These are now mapped as 'cancel keys'.
Simplify determining cancel keys by subtracting alpha_buffer_keys from default cancel keys.

I hope this change will make the keyboard mappings more robust since it
can no longer miss unmapping keys.