Adds support for metadata to the surface APIs

- received metadata is visible on the ActiveCall object
- metadata to send is keyword args on ActiveCall objects

Also
- fixes a typo that meant that the wrong error error code might be returned
- fixes bad references in some tests that are only visible when run via rspec
	Change on 2014/12/10 by temiola <temiola@google.com>
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=81811008