The resource create and update methods now accept keyword arguments

of the form extra_data__field_name which are rewritten to

extra_data.field_name so that Review Board can understand them. This

occurs because extra_data.field_name cannot be used as a keyword

argument, so all extra data field updates have to built into a dict,

which must then be splatted into the appropriate method.
Unit tests have been updated that cover both methods.

Ran unit tests.