Allow 'q' to close buffer

[m42e]

This will enable 'q' to close the list buffer.

[FiXato]

Looks fine to me, even though alphanumeric characters might make it a bit trickier to later implement keyword filtering of the list.
Then again, I'm no longer actively developing/maintaining this script (I see I still have to merge in Flashcode's changes to make it python3 compatible), so I'm not sure if it's likely I'll ever implementing that filtering anyway. :)

I'll try to look at merging your PR later this week, as well as updating it for python3, and getting the update to the official weechat repo.