Before introducing InSpec profiles in https://github.com/chef/inspec/pull/252 we had `metadata.rb` keep all information. This included an undisclosed field called `supports`. However, this field was never actually used in practice. So for legacy profiles, this means that `supports` was ignored. In order to keep old profiles running in exactly the way they were before, ignore this field when reading from metadata.rb
For reading the profiles metadata, we're using the train mock backend
through Inspec::Runner. The new `supports` feature never agrees with the
mock backend.
Now, it we figure out if this is a mock class and then just say that it
supports whatever we're asking for.
Tl;dr: there's probably a more beautiful solution to this.
Added a test case, but it fails -- while the command line interface
works fine.
