Use natlas' libnmap instead of the unmaintained libnmap

[0xdade]

Drafting to start to show it works, but we shouldn't merge this until natlas/python-libnmap gets detached to a standalone repository. Once we do that, I'll change the repo name and setup deployment to pypi so that we can pip install it like normal, probably under the name natlas-libnmap.

When this lands it will close #299

[codeclimate]

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[0xdade]

@ajacques Hey look the underlying library has tests and even has an explicit test for the payload that resulted in the CVE

https://github.com/natlas/natlas-libnmap/blob/master/libnmap/test/test_new_parser.py#L7-L16

The library isn't setup in CI yet, but that shouldn't freeze this PR imo.

[ajacques]

Why do so many hashes change when we install one new package?

[0xdade]

The top hash is a hash of all the packages installed, I think. Then more hashes are changing because versions are getting bumped automatically per the rules in Pipfile which mostly say either "*" which matches any version, or ~=x.x which matches any compatible version. We could make this happen less often by restricting to specific versions in Pipfile, though I don't think there's any particular value in that.