www/py-requests-oauthlib: Update to 0.5.0

• Update PORTVERSION and distinfo checksum (0.5.0)
• Update TEST_DEPENDS
• Remove TESTS option since the framework now supports TEST_DEPENDS,etc
• Rename test target and use canonical/wrapped PYDISTUTILS_SETUP variable.

Changes:

https://github.com/requests/requests-oauthlib/blob/v0.5.0/HISTORY.rst