Make links between the project repo and project docs.

[nbanion]

Add details that link the project repo to the project documentation.

• [x] Link to the docs from the README.
• [x] Link to the project repo from the docs.
• [ ] Automate documentation to build when the master branch moves.
• [x] Add a badge to show the documentation build status.

[nbanion]

Here are instructions to set up a webhook that automatically updates the documentation when the master branch adds new commits. I think a repo administrator needs to do it.