NS1 release of v0.24-7 upstream (unchanged)

Creating a source distribution so we can easily install this via Pip. That's until the upstream releases 0.24-7 (or greater) into PyPI.

Steps to create release:

• Checkout repo on branch you want to release. (This was created from master.)
• In the top-level pysubnettree folder do: python setup.py sdist. This will create the release tarball in pysubnettree/dist.
• Attach that tarball to this release tag.
• Done.