Vitalsource Bookstore integration

Option to buy / save content in your account to annotate over in web app. E.g. bringing doc drop hosting in web app.

This ties in with the VitalSource integration:

Hypothesis is considering launching a bookstore to sell books and increase the surface area of content that can be annotated socially, potentially incorporating VitalSource's extensive book coverage. Testing and experimentation will be necessary to determine the viability of this solution.

Not top priority - look to do over next year or so.