Use Travis CI to deploy docs on push

Use Travis CI to deploy the docs to S3 when changes are pushed
to GitHub. I set things up following the instructions at
http://docs.travis-ci.com/user/deployment/s3/

I also cleaned up a few small errors in the rst formatting of the
docs to minimize warnings to make debugging the automatic build
process easier.  These warnings were mostly things like unescaped
asterisks and improper indentation of code blocks.

Finally, I aded vim .swp files to the .gitignore.