Corrected Python v2 non-unicode string issues introduced in v0.6

The Python v2 & v3 compatibility changes made the v0.6 release introduced an issue where non-unicode strings would fail the API method's type-checking assertions. This issue slipped by the test suite because the test suite had been simultaneously updated to use the Python-Future module (which as used ensured unicode type consistency in both Python v2 & v3).

We have removed the Python-Future use from the test suite (so we are testing with more 'native' Python v2 and v3 code), and corrected the issue with the package's type-checking assertions.

Sorry for any headaches you might have had over the weekend (since the v0.6 package was released), upgrading to v0.6.1 should correct this issue.

As always, please do open an issue if you are experiencing any problems or challenges working with the ciscosparkapi package.

-Thank You!