Bootstrap docs site

[lifenautjoe]

Move the readme for both https://github.com/OpenbookOrg/openbook-api and https://github.com/OpenbookOrg/openbook-app to the docs website and deploy it.

[jozsefsallai]

Done in 6a8a23d. You may edit the content and restructure stuff to your liking! :) Not closing the issue just yet.