Replace `make` stuff to python stuff

Fixes #1618.

This PR was created to simplify #1579 . Its objective is remove `make` stuff as the repository will be fully pythonic. 

Detailed changes in logic order:
- Remotion of custom targes from CMakeLists.txt
- Readme updated with python instructions

CC: @oxtopus @rhyolight @scottpurdy 
> The run_tests.sh is there because of a policy at Numenta to have consistent entry points for invoking tests.

setuptools.setup has a `entry_points` parameter which allows we specify python scripts to be installed in the system and may be called in everywher on shell only typing its name. This is the case of `nustudio` on nupic.studio:

https://github.com/nupic-community/nupic.studio/blob/master/setup.py#L37

I simply type `nustudio` on the shell (not matter from where I call it) and voilá! NuPIC Studio is executed!

I belive that this is the right way to call entry points in the Python projects.