created new track_search binding to allow searching for tracks (really recordings). Modified existing model classes to call super() to handle search (open/closed principle, attempting to reduce duplicate code). Fixed xml namespace issue in specs.
Merge branch 'track_search' of https://github.com/tomwolfe/musicbrainz into tomwolfe-track_search
Require date to avoid CI exception 'wrong number of arguments(3 for 0)'. #18