Rename _config.yml to _config.example.yml.

Ignore the real config. This is in preparation for templating _config.yml
during the Ansible build.
Use the hardcoded config as a default.

This will build the site properly from Jenkins without having to do a bunch of
ugly templating within the Jenkins job.
Template the Jekyll build in development mode.
set -u
Merge pull request #361 from rackerlabs/compress-in-prod

Generate _config.yml from a template. :shipit: