ENH: raise an error on recursive subprocess

This feature attempts to raise an error when subprocesses are spawned
recursively, as under Windows when people don't protect their code.
DOC: document __main__ behavior
ENH: compat Py2.X/Py3.X
DOC: formatting
ENH: no pre_dispatch for lists
Changed minus sign to plus sign in docstring.
Merge pull request #54 from ApproximateIdentity/documentation-n_jobs

Changed minus sign to plus sign in docstring.
MISC: update changelog
REL: release 0.7.0a
Python 2.5 is no longer supported
BUG: fix recursive fork detection under windows
REL: joblib 0.7.0.b
BUG: fix hash collision

And add a warning when things go wrong
TEST: more hash tests
REL: joblib 0.7.0c
BUG: fix corner-case hashing in Python 3
REL: release 0.7.0d
DOC: document the supported Python versions
typos in joblib/numpy_pickle.py
typos in joblib/memory.py