/cc @rasa

post-processor/vagrant: skip gzip compression if compression_level=0

website: fix run-on italicizing for description of data_bags_path

underscore of "data_bags" should be escaped; causes run-on italic

website: Fix spelling in Intro documentation

core: log golang version in debug output

This introduces a Docker builder. The docker builder is able to create
containers by starting an existing Docker image, provisioning it using
standard practices, and then exporting it using `docker export`.

website: Fix missing whitespace. [ci skip]