Replace "run_tests.sh" to the cross platform "run_nupic_tests"

This PR aims replace `run_tests.sh` to a more cross platform and default approach.

It allows any user type `run_nupic_tests` in everywhere on shell and have access to all nupic tests (of course, default install location should be specified on $PATH). Example:

`$ run_nupic_tests --help`