Supermarket is live, use it for Berks source

With the Supermarket "Grand Opening"[0], we should use it as the
default source for Berksfiles.

[0]: http://www.getchef.com/blog/2014/07/03/supermarket-grand-opening/
Update the content checksums for supermarket source

The Berksfile contents cause specs to fail because the content is
different and we used the checksums generated, so they needed to be
updated.
Merge pull request #112 from opscode/jtimberman/supermarket-berks-source

Supermarket is live, use it for Berks source