feat(buttons): add checkbox and radio buttons

[pkozlowski-opensource]

Closes #53

Hopefully this one is not very controversial / easy to review.

[joshdmiller]

@pkozlowski-opensource Awesome.

This is why I love AngularJS - the tests are longer the directives!

[SidhNor]

@pkozlowski-opensource looks great to me. Really simple and clean

[ajoslin]

Wow, super simple. Nice @pkozlowski-opensource ! 👍

94 lines of tests and 73 lines of code. As @joshdmiller said, AngularJS wins 😄

Only one thing - can we make the event for changing the buttons a config value, defaulting to click?

eg element.bind(buttonConfig.toggleEvent, function() { - so on mobile we can replace click with a tap event :-)

I just can't think of a good name for the config value.. changeEvent, toggleEvent, maybe even just clickEvent?

[pkozlowski-opensource]

Yeh, AngularJS rules the World :-)

Sure, let's make the events configurable, toggleEvent sounds nice if you ask me.

[petebacondarwin]

actionEvent although I think toggleEvent is better.

[petebacondarwin]

Actually, is this removal of hard-coded "button" events something that should be dealt with throughout?
Igor was talking about best practices with directives recently and he suggested that click/tap was abstracted to some action event - even so far as to use ng-action rather than ng-click, etc.

[pkozlowski-opensource]

Landed as 571ccf4

For now added a config option for the toggleEvent as pointed out by @ajoslin but I agree with @petebacondarwin that we should start thinking about encapsulating it in a more generic way.