Automatically build documenation and deploy to gh-pages branch

[stephendolan]

This PR tackles the following:

• Remove the committed documentation
• Add /docs/ to .gitignore
• Add documentation link in the README

This will close #8

@confact, all you'll need to do once we merge this is wait for the GitHub action to finish, then point the GitHub docs in the repo settings to the gh-pages branch! You don't have to set the directory to serve from to docs or anything. Here's a screenshot from Pundit:

[confact]

@stephendolan looks great! LGTM