fix for when _user is not defined.

calling getattr on unset property in python 3.3 throws an exception
added default platform values for known properties

currently when parsing a github or bitbuck or any other known platform
the _user property is not being set. this is because it is not in the
pattern/format since it is always known. i added a way for setting
default property values for known platform properties. i also updated
the test and ran them. all passed.
Merge pull request #2 from tony-osibov/_user-fix

_user fix