TumblrShareUtils

Lemme know what you guys think. Thinking was as such:

* The `TumblrShareUtils` should be "gistable", meaning the helpful functions should be able to be inside a single (ideally small) file.
* The `DeepLinkCreator` will give back Uris instead of the Intent like the `ShareIntentCreator`. The thought here was that they could be used for anything else that the dev wanted to, even if that wasn't immediately opening Tumblr.