Test cases for prototype (and some linter cleaning)

[admosity]

Added some test cases for using prototype.

1. Test case for method override (more of an example than spec).
2. Test case for propagating content when using prototype.

Commenting out

expect(elementB2.firstElementChild.nodeName.toLowerCase()).toEqual('span');

passes the test.

[admosity]

Added some test cases for mixins, but can't seem to replicate the issue I'm having. I think in my case the lifecycle triggers from the mixins aren't firing. Will add some test cases with lifecycle hooks.

[admosity]

The lifecycle hooks are not triggering when using a prototype with mixins.

[csuwildcat]

I have retooled the mixin section of the test spec to cover your cases (I think). If there are any outstanding, I will gladly accept a new commit with any I may have missed :)

[csuwildcat]

I believe I incorporated the meat of this into the code - if not, let me know and I will address the remaining.