* Add a new, simplified version of pipstrap.
* Use tools/pipstrap.py
* Uncomment code
* Refactor pip_install.py and provide hashes.
* Fix test_sdists.sh.
* Make code work on Python 2.
* Call strip_hashes.py using Python 3.
* Pin the oldest version of httplib2 used in distros
* Strip enum34 dependency.
* Remove pip pinnings from dev_constraints.txt
* Correct pipstrap docstring.
* Don't set working_dir twice.
* Add comments