Support for NSMapTable

[hfossli]

Pretty much the same as NSDictionary categories.

[zwaldowski]

Thanks for the contribution! -match: should compose using -each: and -apply: shouldn't be implemented since we can't concurrently enumerate a map table. All category methods should be prefixed using bk_ and it is not mergable with master. If you would rather not make those changes, we could ourselves in short order.

[hfossli]

Ah. Now I get why this has conflicts with master. My fork is based on June 2013.. Haha. That's why I didn't see any prefixes in the NSDictionary+BlocksKit implementation which again lead me to think some magic added those prefixes..

I will totally create a new pull request tomorrow.

[hfossli]

Okay, a new pull request is now open at #272. I removed -apply: as you suggested. -match: should IMO not use -each: because stopping the iteration is IMO important.

[zwaldowski]

Right, silly me. Wasn't thinking. Thanks!