run tests_run in parallel

python pytest-xdist; we haven't been using this;
tests_run_all seem to fail with this (Swarming already)
add external cmake module to determin number for CPU cores
execute python unittests in parallel

pytest-xdist -n
Merge branch 'master' into parallel_unittests
Revert "add external cmake module to determin number for CPU cores"

This reverts commit f46362b6e31fd460d5149a812c4c36d2b11fac92.
Revert "execute python unittests in parallel"

This reverts commit a05f97b4013971e5cf0229b07b0ab018ed6bf3b6.
parallel tests: use harcoded 2 threads

not much improvement was observed otherwise.
Merge branch 'master' into parallel_unittests

Conflicts:
	CMakeLists.txt
fix mistake in merge
Merge branch 'master' into iss389

Conflicts:
	nupic/frameworks/opf/exp_generator/__init__.py
	nupic/frameworks/prediction/GUIs.py
	nupic/frameworks/prediction/callbacks.py
	nupic/frameworks/prediction/experiment.py
	nupic/frameworks/prediction/experimentdeschelpers.py
	nupic/frameworks/prediction/helpers.py
	nupic/frameworks/prediction/postprocess/__init__.py
	nupic/frameworks/prediction/postprocess/classificationstats.py
	nupic/frameworks/prediction/postprocess/inputpredictionstats.py
	nupic/frameworks/prediction/postprocess/knnregressionstats.py
	nupic/frameworks/prediction/postprocess/linearregressionstats.py
	nupic/frameworks/prediction/postprocess/ngramstats.py
	nupic/frameworks/prediction/postprocess/poormanstats.py
	nupic/frameworks/prediction/postprocess/postprocess.py
	nupic/frameworks/prediction/postprocess/spstats.py
	nupic/frameworks/prediction/utils.py
	nupic/regions/CLARegion.py
	nupic/regions/CLARegionSimple.py
Adding retry to pip install
Merge pull request #964 from jaredweiss/iss389

Issue #389: removing old LPF code
Merge pull request #976 from rhyolight/retry-pip-install

Adding retry to pip install