Add README, including docs describing how to synchronize with CPython.

README.rst

+Python Module Distribution Utilities extracted from the Python Standard Library
+
+Synchronizing
+=============
+
+This project is kept in sync with the code still in stdlib.
+
+From CPython
+------------
+
+The original history and attribution of all changes contributed to CPython can be found in the `cpython branch <https://github.com/pypa/distutils/tree/cpython>`_. If new commits are added to CPython, they should be synchronized back to this project.
+
+First, create a clone of CPython that only includes the distutils changes. Due to the large size of the CPython repository, this operation is fairly expensive.
+
+    git clone https://github.com/python/cpython python-distutils
+    cd python-distutils
+    git filter-branch --prune-empty --subdirectory-filter Lib/distutils master
+
+Then, pull those changes into the repository at the cpython branch.
+
+    cd $distutils
+    git checkout cpython
+    git fetch $python_distutils
+    git merge FETCH_HEAD
+
+Finally, merge the changes from cpython into master (possibly as a pull request).
+
+To CPython
+----------
+
+Merging changes from this repository is easier.
+
+From the CPython repo, cherry-pick the changes from this project.
+
+    git -C $distutils format-patch HEAD~2 --stdout | git am --directory Lib
+
+To Setuptools
+-------------
+
+This project also maintains a `clean branch <https://github.com/pypa/distutils/tree/clean>`_ to capture only the code changes to distutils, excluding the ancillary details like packaging and this document.