mattdrayer/api-middleware-regex: Support for opaque keys, server API nam...

@chrisndodge @antoviaque, I think I've finally gotten to the bottom of the failing LMS tests.  In troubleshooting I went ahead and added the "server" namespace to the root URI as I mentioned earlier today.  So, @martynjames, FYI that you'll need to update Apros to reflect the new path (/api/server/courses, etc.) after this PR has been merged.

Chris and I discovered that the social metrics test fails due to a failed mock when running the suite via paver, however it passes when running via rake -- very odd.
If I put the user_api line back where it was, the tests resume their failed state.  I've now pulled it out from the feature flag closure and positioned it just below, which keeps the tests green and breaks the dependency on our configuration.