Parsing requirements.txt -> setup install_requires

This will get the dependencies written into whl files when packages, but doesn't really serve any other purpose at this point because users will still need to manually install the requirements via `pip -r`.

Fixes #1636.
Importing pip means that people won't be able to install nupic without it (`python setup.py` or `easy_install`). Since we just want the text from the file, why not this:

```
with open(os.path.join(repositoryDir, requirementsFile)) as f:
  requirements = [line.strip() for line in f]
return requirements
```