Remove HtmTest

Fixes #1620.

Depends on https://github.com/numenta/nupic.core/issues/255 to add tests to nupic.core.

This PR was created to simplify #1579 . Its objective is remove HtmTest which is a redundant test and also helps to reduce the number of extensions to setuptools handle (as far I know setuptools doesn't build executables).

The integration tests bellow already play well the role of HtmTest:

https://github.com/numenta/nupic/blob/master/tests/integration/nupic/engine/network_testnode_interchangeability.py
https://github.com/numenta/nupic/blob/master/tests/integration/nupic/engine/network_twonode_test.py

CC: @rhyolight @scottpurdy