Pysubnettree

* Use devN style format in setup.py (Arne Welzel, Corelight)

Commit aa205cfa996d166ae54ce5fdcebaf4b310301a34 switched this to .postN
format, but update-changes only recognizes .devN, so switch to that in
order to make automatic updating of setup.py versions work again.

* GH-15: GH-32: GH-33: SubnetTree: Update swig generated files (Arne Welzel, Corelight)

* Update cmake submodule to deprecate FindRequiredPackage (Tim Wojtulewicz, Corelight)

* Require CMake 3.15 for consistency with other Zeek projects (Tim Wojtulewicz, Corelight)

* Fix python variable usage in configure (Tim Wojtulewicz, Corelight)

* Use find_package instead of FindRequiredPackage (Tim Wojtulewicz, Corelight)

* Use new-style version numbers for setup.py (Tim Wojtulewicz, Corelight)

* Remove old travis CI configuration, add new Github workflow instead (Tim Wojtulewicz, Corelight)

* Update patricia files to match Zeek's newer version (Tim Wojtulewicz, Corelight)

* Update CMake logic to prefer Python 3 over Python 2 (Jon Siwek, Corelight)

* Update minimum required CMake to 3.5 (Jon Siwek, Corelight)