Add .travis.yml
Add .travis.yml

The build bachines at travis-ci are using old ubuntu installations, and
these installs don't ship the bootstrap theme we're using for the book,
so try installing it with pip in a virtualenv instead.

containerbook/containerbook,jonte/containerbook,containerbook/containerbook,jonte/containerbook,containerbook/containerbook,jonte/containerbook,containerbook/containerbook,jonte/containerbook