fix!: drop support for Python 2.7 / 3.5 (#212)

Drop 'six' module

Drop 'u"' prefixes for text

Remove other Python 2.7 workarounds

Drop use of 'pytz'

Dxpand range to allow 'google-auth' 2.x versions

Remove 'general_helpers.wraps': except for a backward-compatibility
import, 'functools.wraps' does everything wee need on Python >= 3.6.

Remove 'packaging' dependency

Release-As: 2.0.0b1

Closes #74.

Closes #215.
35 files changed