A symbol should be converted to a string when being encoded into a Data object.
Symbols are now treated as Strings when they're put into a Data instance.
Commit 1509029 from Darryl L. Pierce in branch 'proton/trunk'
[ https://svn.apache.org/r1509029 ]
PROTON-381: Fixed encoding a Ruby symbol into a Data object.
The symbol is converted to a String before being added the Data