Fixed the description of the tracker test.
Renamed the Tracker class to Metainfo to reflect its role.  Fixed the reference to the test torrent file.
Announcing a torrent to a tracker and receiving a response with a list of peers now succeeds.  There is an end-to-end test for this, but it only asserts that at least one peer has been returned for the ubuntu torrent.  It is a non-deterministic test.  The non-determinism is annoying as is the requirement of a network connection to run the test.