Implement to setuptools installable package

[dspruell-s01]

Would be great to have tls_prober be installable from PyPI, via pip, in virtualenv with ease, etc.

https://packaging.python.org/tutorials/packaging-projects/

[tomato42]

1. location of fingerprints would have to be abstracted
2. generation of new ones -a option would nee to create them in a current working directory, /tmp, or someplace similar

[dspruell-s01]

If I'm not mistaken fingerprints can be included in the package and access abstracted using the ResourceManager API in setuptools as mentioned here: https://setuptools.readthedocs.io/en/latest/userguide/datafiles.html#accessing-data-files-at-runtime

Regarding -a, could maybe see having a system database (installed with the package, read-only) and a user database (in XDG_DATA_HOME or a path from env var) that is modifiable, and having those merged at runtime or something.

[tomato42]

sounds good, feel free to propose a PR with this

maybe split it up to two PRs to make review a bit easier