Drop support for EOL Python 2.7-3.4

[hugovk]

Same as #67 but also drops support for EOL versions.

• https://devguide.python.org/#status-of-python-branches
• https://devguide.python.org/devcycle/#end-of-life-branches

[adrienverge]

I know Python 2 was recently sunset, but I don't see the need to drop support now, if it still continues to work. Is the code simplification it brings the only reason, or do you have another one?

[hugovk]

Yeah, you can keep it if you like, maybe not as big benefits for this project as for others.

Here's some reasons:

• Security:
  • Python 2.7 is no longer maintained and won't have any new security vulnerabilities fixed
  • Pillow no longer supports Python 2.7, and the last release for 2.7 doesn't have security fixes
  • PyCairo no longer supports Python 2.7
• You can start to use new Python features without worrying about old versions
• Use fewer CI testing resources
• It's becoming less and less used or relevant: https://github.com/hugovk/pypi-tools/blob/master/README.md#examples

[adrienverge]

OK, you convinced me. Can you please rebase on latest master?

[hugovk]

Rebased!