Delete ez_setup.py
ez_setup.py is few years out of date, we should stop distributing it.

Up to date versions of Python 2 and 3 provide setuptools and pip out of the box `python -m ensurepip --upgrade`. For other Python versions, we can simply point users to the up to date instructions at https://packaging.python.org/en/latest/installing.html#requirements-for-installing-packages.
