BLD: Stop distributing ez_setup.py, #10168

The distributed version of ez_setup is few years out of date and the python
packaging world is a fast moving target.

Recent versions of Python 2 and 3 provide setuptools and pip out of the box.
For other Python versions, we can point users to the official and up to date
instructions at

https://packaging.python.org/en/latest/installing.html

Author: andreabedini

doc/source/install.rst

@@ -212,6 +212,7 @@ installed), make sure you have `nose
 Dependencies
 ------------
 
+* `setuptools <http://pythonhosted.org/setuptools>`__
 * `NumPy <http://www.numpy.org>`__: 1.7.0 or higher
 * `python-dateutil <http://labix.org/python-dateutil>`__ 1.5 or higher
 * `pytz <http://pytz.sourceforge.net/>`__

ez_setup.py

@@ -27,14 +27,8 @@
 except ImportError:
     _CYTHON_INSTALLED = False
 
-# try bootstrapping setuptools if it doesn't exist
 try:
     import pkg_resources
-    try:
-        pkg_resources.require("setuptools>=0.6c5")
-    except pkg_resources.VersionConflict:
-        from ez_setup import use_setuptools
-        use_setuptools(version="0.6c5")
     from setuptools import setup, Command
     _have_setuptools = True
 except ImportError: