CleanUp for `toBeInTheDom` and `toHaveTextContent`

[antsmartian]

Following up the conversation on #44, looks like we need to do bit of clean up on toBeInTheDom and toHaveTextContent on the jest extensions. I can pick this up and finish this task.

@gnapse Let me know if you have already picked this up.

[gnapse]

I started this in #46, and only after that I saw this.

[antsmartian]

Alright, @gnapse this should be given to this library now : https://github.com/kentcdodds/dom-testing-library :) :)

@kentcdodds Thats a very cool move. In fact I was thinking, how we could decouple the library, so that one can reuse the DOM queries alone and exactly you had done this! This is awesome.. Cheers! 💯

[kentcdodds]

Thanks! Sorry it means that y'all's PRs need to be moved over to the other package. Hopefully it should be pretty straightforward though.

[antsmartian]

@kentcdodds No problem, will move them.. Let us know once you completely decouple the codebase and done with your work.

[kentcdodds]

I'm finished actually. react-testing-library has already been updated!

I'm hanging out with the family this weekend so I may not get to your PRs right away.

[antsmartian]

Perfect, will give the PR over there in sometime!