Add simple Rake task for testing 0.8.x w/ docker
Update Chef versions & Ruby versions for Travis

Run the last patch release for each previous version of Chef 11, and
only run for the Ruby version that is packaged with each version, i.e.
Ruby 1.9.3.
Lock rspec versions in `gemfiles/Gemfile*`

Travis keeps installing 2.99 which apparently doesn’t work.
Update ChefSpec to v4.0.0
Lock ChefSpec to v3.4.0 in gemfiles

This should work, hopefully?
Include Chef v11.10.4 in Travis
Lock RSpec to v2.14.1 in gemfiles
Syntax errros with chef-server 11.8 fixed.