Remove ez_setup from documentation (#1553)

Remove ez_setup from setuptools installation docs
    
This removes ez_setup.py from the setuptools development instructions
and updates some links into EasyInstall that were skipping over the
deprecation warning.

changelog.d/1553.doc.rst

+Update installation instructions to point to ``pip install`` instead of ``ez_setup.py``.
\ No newline at end of file

docs/setuptools.txt

@@ -73,23 +73,17 @@ Developer's Guide
 Installing ``setuptools``
 =========================
 
-Please follow the `EasyInstall Installation Instructions`_ to install the
-current stable version of setuptools.  In particular, be sure to read the
-section on `Custom Installation Locations`_ if you are installing anywhere
-other than Python's ``site-packages`` directory.
+.. _EasyInstall Installation Instructions: easy_install.html
 
-.. _EasyInstall Installation Instructions: easy_install.html#installation-instructions
+.. _Custom Installation Locations: easy_install.html
 
-.. _Custom Installation Locations: easy_install.html#custom-installation-locations
+.. _Installing Packages: https://packaging.python.org/tutorials/installing-packages/
 
-If you want the current in-development version of setuptools, you should first
-install a stable version, and then run::
+To install the latest version of setuptools, use::
 
-    ez_setup.py setuptools==dev
-
-This will download and install the latest development (i.e. unstable) version
-of setuptools from the Python Subversion sandbox.
+    pip install -U setuptools
 
+Refer to `Installing Packages`_ guide for more information.
 
 Basic Use
 =========