* Bumps to wolfSSL 5.1.1
* Fixup `make clean`
* Move `wolfssl` src to root
* Switch test from DigiCert to GlobalSign (`python.org` ditched DigiCert
years ago)
* Make SSLContext call `wolfSSL_Init()` which fixes a few issues
* Make `setup.py` compile CFFI and wolfSSL C code
* Fully enable SSLv3 support
* Add TLSv1.3 support
* Fix bug in `wolfSSL_Free()` usage
* Update `tox.ini` to a currently supported platform