BF: Avoid closing "/dev/urandom" for Python 3.4.0

Upstream bug: http://bugs.python.org/issue21207

Closes gh-687
DOC: ChangeLog entry for Python 3.4.0 persistent "/dev/urandom" fix
Merge pull request #714 from kwirk/urandom-persistent

BF: Avoid closing "/dev/urandom" for Python 3.4.0