v2.8.0 - Composability

* ContentViewFactory added a herusitic other than instanceof, `typeUrn`, so that it can create ContentViews for content constructed from outside this lib.
* Content Types have a `typeUrn` property
* Builds: Wrap in a UMD-ish fragment that should make the builds loadable with Livefyre.require, require, or by exporting a browser global at `Livefyre['streamhub-sdk']`.