Pysubnettree

* Fix compile error with Python C API. Addresses 887. (Matthias
Vallentin)

* Fixing memory leak. When deleting a PySubnetTree, the values
weren't unref'ed. (Simon Arlott)

* pysubnettree now supports IPv6 addresses and prefixes. (Henry
Stern, updated by Daniel Thayer).

* SubnetTree now have a binary mode as well in in which single
addresses are passed in the form of packed binary strings as,
e.g., returned by `socket.inet_aton. (Henry Stern, updated by
Daniel Thayer).

* Raise minimum required CMake version to 2.6.3 (Jon Siwek)

* Fixing compiler warnings. Addresses 388. (Jon Siwek)

* Install binaries with an RPATH. (Jon Siwek)

* Add check for incompatible swig+python versions. Addresses 562.
(Jon Siwek)

* Workaround for FreeBSD CMake port missing debug flags. (Jon Siwek)

* Release 0.37.