Adds h5py.__version__, fixes #254
Fix memory leak in _errors.pyx
Avoid exceptions in control flow in _objects.pyx
Merge pull request #256 from ddale/version_str

Adds h5py.__version__, fixes #254
Merge __version__ string from branch '2.1'
Merge pull request 258 (fix for memory leak)
Initial implementation of mz5 support.