py.test-base test runner.

This requires some minor fixing-up of python namespaces to avoid namespace
conflicts with pre-existing py module.
Install py.test via pip during build
Remove dependency on nose
Moving requirements.txt and adding comments following feedback at https://github.com/oxtopus/nupic/commit/fb23e3558f7bda214ba424ae26bdced47f0419a3#commitcomment-3705875
Moving run_tests.py to bin/ to match post-build testing instructions in README.md
Run tests in verbose mode
Merge pull request #131 from oxtopus/pytest-requirements.txt

py.test-based test runner
Explicitly write out init_cov_core.pth to overcome a problem with cov-core setup.py install
Documentation added to explain added line in build.sh
Merge pull request #133 from oxtopus/pytest-cov-core-hotfix

Explicitly write out init_cov_core.pth
Not throwing error in cleanbuild.sh if temporary folder to be removed doesn't exist
Merge branch 'master' of git://github.com/numenta/nupic
pip as a dependency for python modules
modular: update Readme, list dependencies and platforms
fix configure.ac bug in HAVE_PIP
fix proper AM_CONDITIONAL use in configure.ac for pip
changes to Readme based on comments to PR

thanks
Install python packages from repository cache instead of from PyPi directly.

This will make it possible to build without needing an internet connection,
speeding things up as well as maintaining better control.
Merge remote-tracking branch 'breznak/pip-install' into cached-externals
Minor spelling correction