Move consumer atom feed to correct API location.

When fetching info specific to a consumer our preferred API layout is to
go to /consumers/{uuid}.

This patch moves /owners/{key}/consumers/{uuid}/atom to
/consumers/{uuid}/atom.

This coincides also with /consumers/{uuid}/events which is just a
different representation of the same data.

I have verified the old API call is used in neither SAM, Satellite,
nor hosted environments.

Updated and expanded on some related spec tests.
Improve spec test for running in parallel.
Use XPath to verify event atom feed looks correct.
Merge pull request #398 from candlepin/dgoodwin/consumer-atom-relocation

Move consumer atom feed to correct API location.