unbind method + unit tests + method argument

[bfirsh]

This is building upon #65 and #69. I've added a "method" argument so you can specify exactly which handler to remove, like in most event systems (e.g. on('event', method) / off('event', method)).

There's a bit of undefined behaviour in the unbind method which needs a design decision though. If the scope is not set, then calling just unbind('a') will only remove handlers for "a" in the current scope. I think I'd expect it to remove all handlers for "a", like calling off('event') in an event system. Thoughts?

[bfirsh]

It also doesn't take into account comma-separated keys or modifiers. I'm doing some work on that now, but it means teasing out the parsing code from assignKey().

[sandinmyjoints]

This is much needed. Thanks for working on it. I'd vote for unbind('a') to remove all handlers, since you can already get the other functionality by supplying the scope: unbind('a', curScope).

[OliverJAsh]

+1