Replace book-viewer

[VocAddict]

The repository has not been updated since August 2016 so it might be best to implement an internal version of it instead of mkaing changes on a fork of book-viewer.

[VocAddict]

Okay, it's been a while since I've touched this but for now I'm going to be using the existing implementation just to get the project off the ground while I work on a fork of book-viewer more tailored to this project or maybe an entirely new one to replace it with.