Continued fleshing out the DirectMessage class.
Use get_object_vars instead of get_class_vars so we get the current array representation rather than the default one.
Adds some docblocks.
We don't want nulls in our toArray() result, so filter them out.
Remove equals() and notEquals() functions as they're not necessary to translate from the Python lib.
Merge pull request #1 from primitive-type/direct-message

Continued fleshing out the DirectMessage class.