Merge pull request #140 from t-8ch/ssl_verify_hostname

Manual specification of hostname to verify against.
Update CHANGES.rst
Adding 'urllib3.contrib' to setup.py (#167)
Tests for bad Content-Type type.

Content-Type should be returned as a native string, not a bytestring.
This commit ensures that all current tests that exercise the encoding
fail on Python 3, where native strings aren't bytestrings.
Return native strings for header-values.
Merge pull request #168 from Lukasa/content_type

Content-Type header values should be native strings.