Merge branch 'release-0.10' into develop
Ezid::Metadata.register_element defines reader and writer methods
(instead of relying on #method_missing).
Added Ezid::Metadata.unregister_element private class method,
mainly to support testing.
Merge pull request #31 from duke-libraries/defined-metadata-methods

Ezid::Metadata.register_element defines reader and writer methods
Version 0.11.0
Merge branch 'release-0.11'