Support pip version 10.0 and greater

[conscott]

What current issue(s) does this address, or what feature is it adding?
setup.py currently fails with pip version >= 10.0 due to some module path changes

How did you solve this problem?
Add code for correct import path in pip verisons >= 10.0

How did you make sure your solution works?

pip install pip==10.0
python ./setup.py  # no import error in branch, fails on development/master

pip install pip==9.0.3
python ./setup.py  # no import error in branch, successful on development/master

Are there any special changes in the code that we should be aware of?
no

Please check the following, if applicable:

• Did you add any tests?
• Did you run make lint?
• Did you run make test?
• Are you making a PR to a feature branch or development rather than master?
• Did you add an entry to CHANGELOG.rst? (if not, please do)

[coveralls]

Coverage remained the same at 79.409% when pulling 4046665 on conscott:pip_version_support into 19e8f76 on CityOfZion:development.

[metachris]

Thanks! 👍