TLS Canary experimental release: 3.3.0a1

This is an experimental release that incorporates various fixes for nightly regressions which are becoming increasingly frequent. Also this version now requires python3. Python2 support is dropped completely.

This release is not available through regular PyPI. To install it via pip, you must use testpypi as package resource:

$ pip install -i https://test.pypi.org/pypi tlscanary --pre