Python 2.7 and 3.5 EOL

[jamesmyatt]

Python 2.7 and 3.5 are both EOL. Can they be removed from the supported Python versions and the build matrix?

Adding python_requires=">=3.6" to the setup will ensure that only the latest version that supports 2.7 or 3.5 will be installed via pip on those platforms. This means that the old versions will continue to be available but new features will only be available for Python 3.6+

https://packaging.python.org/guides/distributing-packages-using-setuptools/#python-requires

[jamesmyatt]

Closed by #63