Updated test documentation
Update test readme file
Update functional test README file
Removed config secrets from travis setup, since we're now only running the unit tests
PyLint fixes
Ensure files are closed properly, to avoid Python3 warning
Ensure the test file is closed after use to prevent Python3 warnings
Unit test fixes for Python3 support
Monkey-patch httpretty for Python3 support

This fix is in the httpretty codebase, but not yet released
requests-oauthlib 0.3.2 introduced a Unicode bug.

Hold back to 0.3.1 until this is resolved
Travis now tests all supported Python versions
Latest requests_oauthlib fixes a Unicode bug, so we don't need to ask requests to decode anymore