Ported testium2 to the actual testium repo

This is the somewhat/mostly complete port of testium to what is generally called the "reverse mocha" model. Since this is the product of rewriting testium from scratch while trying to track down weird PhantomJS behavior, this PR is terrible in pretty much every regard. The real commit history can be found in [the testium2 repo](https://github.com/jkrems/testium2). This "rebase" is my attempt to make it "mergeable" even though I'm not sure it actually makes sense to merge this (as opposed to leaving it a separate branch).

##### Highlights

##### Usage / Breaking Changes