PROTON-322: Extend the Ruby Hash class to work with the Data class.

Adds the proton_data_put and proton_data_get methods to the Hash class
for Ruby. When passed an instance of Qpid::Proton::Data it marshals the
contents of the Hash, encoding the values properly.

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/trunk@1490429 13f79535-47bb-0310-9956-ffa450edef68