Remove external dependencies from NuPIC repo

[rhyolight]

Once we have virtualenv repos with dependencies and have updated Jenkins and Travis to use them, we can completely remove external dependencies from the NuPIC repo.

Comments from JIRA

From @breznak:

What are these external deps? Appart from python modules, but those are installed by pip. Then there's swig, but that one is really tricky and old version, so imho should be bundeled.
Boost - but we provide headers only, no need to use whole lib.

From @scottpurdy

Marek, we plan to create pre-built virtualenvs with the deps so that we can get them out of the NuPIC repo. This solves licensing issues and allows them to be pre-built, as opposed to pip cache that requires a build. More details to come later as we are still nailing down the final details and will send an email to the list when we have a better idea.

Associated commits:

https://github.com/numenta/nupic-linux64/commit/42e76f8c31de70cbe92362f8f81dab8a71d2fa31