Improve coverage measurements of multiprocessing functional tests.

Fix pex binary distribution replacing subprocess rendering with
multiprocessing as pex cannot deal with shellscripts on packages.
Major code reorganization, cleanup and code simplification.
Implement simple debug levels. Make default conf.py and index.rst
configurable.

Make travis happy

release 0.7.4

release 0.7.3

release 0.7.2

release 0.7.1

release 0.7

release 0.6