Tags Redux: styling tags

This PR styles the tags closer to what they were before we removed Jquery UI. Personally, I preferred them with some styling to show they were distinct from the annotation body. 
![tags](https://cloud.githubusercontent.com/assets/521978/4004591/9ce489f8-2983-11e4-9c1c-fe5d6ebc0c11.png)

Meant to resolve: https://github.com/hypothesis/h/issues/1426
Why all these properties? Nothing apart from the margin actually does anything here when viewing this in the stream.