Spf3

* publish wheels to PyPI

* add explicit license
* fix syntax warning in Python 3.12+

* Switch to setuptools because "it's the future"
* Rename project to spf3, as it is now a fork

* Fix doctest for CNAME fixes to work with python and python3
* Fix dnspython integration so that SPF TempError is properly raised when
there are timeout or no nameserver errors
* Add missing use of timeout parameter for dnspython DNSLookup
* Restore DNSLookup API for pydnsv(DNS) for tcp fallback works again
* Update Installation section of README.md

* Add support for use of dnspython (dns) if installed
* Catch ValueError due to improper IP address in connect IP or in ip4/ip6
mechanisms
* Fix for CNAME processing causing incorrect permerrors

* Reset void_lookups at top of check()
* Ignore permerror for best_guess()
* Don't crash on null DNS TXT record (ignore): test case null-text
* Trailing spaces are allowed by 4.5/2: test case trailing-space
* Make CNAME loop result in unknown host: test case ptr-cname-loop
* Test case and fix for mixed case CNAME loop, test case ptr-cname-loop