Uif-choicefield - check boxes behaving like radio buttons

[chanm003]

https://codepen.io/chanm003/pen/bqBrzm

Expected Behavior

User should be able to check more than one check box. Model should be an array reflecting which boxes the end user has checked.

Actual Behavior

Checkbox group behaves like a radio button group.
Model is a string.

Steps to Reproduce Behavior

[nightullr]

I have worked on this a bit and nearly done, just need to iron out an issue with a test failing.

[GaryWenneker]

Is it fixed yet?

[andrewconnell]

Since the issue is still open, looks like it's still pending.

[nightullr]

My changes work when I test them in Plunkr, but the specs testing with gulp still fails and I'm not sure why - it's actually my first time working with gulp tests so I'm learning as I go. I'll push my branch to my fork this evening, though, if anyone would like to take a look about how to wrap it up.

Edit: https://github.com/nightullr/ng-officeuifabric/tree/uifchoicefield-482