Update Readme.md to pypy3-2.4.0

Create pypy3-2.4.0

Allowing pip-install to have access to config vars

fix @kennethreitz's mess

Should fix issue https://github.com/heroku/heroku-buildpack-python/issues/181

This reverts commit ee93719b.

Conflicts:
	builds/runtimes/download_python

Support for the new Pypy3 release http://morepypy.blogspot.com

Fix typo in libffi check

Create python-3.4.2

Readme updates to Python 3.4.2 and Pypy 2.4.0

Install libffi for bcrypt as well

Do not fail if buildpack dir is readonly

Create download_python() function to reduce repetition

local PYTHON_VERSION=${1:-2.7.8}

Thanks for the tip.  You learn something new every day.