Fix consumer registration and other miscellaneous fixes.

* Add method to validate option hashes.
* Add debug output method.
* Modify select_from method to yield to a block.
* Force HTTPClient to use basic auth for the BasicAuthClient.  By
  default, HTTPClient only uses basic auth in a request when the same
  request without auth returns a 401.  We do not need or want  to make
  double requests in the BasicAuthClient class.