ndg fix

[jrpope2014]

made changes to versioning info as well as added an import with conditional usage of inject_into/extract_from urllib3 to allow ndg-httpsclient==0.4.0 to be present at the same time as httpretty

[jrpope2014]

Note: The code I used here was implemented by @jmcbailey (to appropriate credit correctly) in reference to the following issue:

#242

[gabrielfalcao]

hey thanks for this, I would love to get this PR merged, but it does not have any automated tests.
Please keep in mind that HTTPretty is trusted by many individuals and organizations and we need to ensure that any changes (whether bugfix or feature) must not break existing behavior.

• If your PR is a bugfix, please add automated test(s) to prove that the bug is reproducible
• If your PR is a feature, please add automated test(s) to ensure that your feature works as expected

PR's without tests will NOT be merged, as I don't have time to debug your code, and write tests in your behalf.

Thank you so much for your time

[iurisilvio]

Current tests break if you have ndg-httpsclient>=0.4 installed. I sent a PR with a tox env to reproduce the issue.

[andrewgross]

Added a PR with tests that fixes the issue, and fixed the master branch. I'll ping gabe and have him do a release when he has a chance.