Task: re-enable alternateport test

[jrfnl]

The BaseTestCase::testAlternatePort() test is currently failing due to an issue with the http://portquiz.net site offering this feature for testing.

As this is unrelated to the actual code in Requests, this should not block merging of PRs and/or the release of Requests 2.0.0, so the test has been temporarily disabled (marked as skipped).

The site owner has been informed via email.

Once a response has been received, we can determine whether to re-enable the test or to see about finding an alternative site to test alternate ports with.