Add doc building to release process
DOCS: Finish sentence
Docs: Added new PHP feature and blank release notes for upcoming release

Followup for 14820c4b.
Tests: skip cpo testing on Mac
Drop custom md5 finder and use only hashlib

This module was introduced so that we could use the md5 function while
Python transitioned from the md5 module to hashlib.  The md5 module was
deprecated in Python 2.5 with the recommendation to use hashlib.

Since Python 2.6 is our new minimum we can safely remove this code.