Missing optional support

Merge pull request #32 from bvic23/try_pmkvo_observer

Extension tests

100 % coverage on Core?

Merge pull request #22 from bvic23/improve_performance

Improve performance

Clenaup

Fix typo

Merge pull request #20 from bvic23/cocoapods

Cocoapods

Merge pull request #18 from vasarhelyia/master

Basic NSTextField extensions

Merge pull request #15 from vasarhelyia/master

Basic AppKit extensions

Merge pull request #14 from bvic23/break_travis

Break travis in PR