PROTON-306: Fixes to the Ruby list helper type for Data.

Ensures that elements from a Ruby array that are encoded as a Proton list
type are properly mapped into and out of the Data class.

Provides a simple map for going from the immediate Ruby types into the
Data class.

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/trunk@1487464 13f79535-47bb-0310-9956-ffa450edef68