Drop support for EOL Python

[hugovk]

Python 2.6, 3.2 and 3.3 are EOL (since 2013-10-29, 2016-02-27 and 2017-09-29 respectively) and no longer receiving security updates (or any updates) from the core Python team.

They're also little used.

Here's the pip installs for gitdb from PyPI for August 2018:

python_version	percent	download_count
2.7	81.86%	108,971
3.6	8.44%	11,233
3.5	7.02%	9,349
3.4	1.55%	2,058
2.6	0.76%	1,005
3.7	0.37%	491
3.3	0.00%	4
Total		133,111

Source: pypinfo --start-date 2018-08-01 --end-date 2018-08-31 --json gitdb pyversion

[Byron]

Thanks a lot! I will see to making a new release today.

[hugovk]

You're welcome!