remove python 3.3 from test environments

[ReblochonMasque]

twisted requires python 3.4+
In relation to PR #95 TravisCI error

[coveralls]

Coverage remained the same at 100.0% when pulling 9da533f on ReblochonMasque:patch-2 into 39a7c6d on glyph:master.

[coveralls]

Coverage remained the same at 100.0% when pulling 9da533f on ReblochonMasque:patch-2 into 39a7c6d on glyph:master.

[coveralls]

Coverage remained the same at 100.0% when pulling 9da533f on ReblochonMasque:patch-2 into 39a7c6d on glyph:master.

[glyph]

Thanks for your contribution.

[hugovk]

Python 3.3 is EOL and no longer receiving security updates (or any updates) from the core Python team, so how about removing instead of just commenting?

Can also remove 3.3 from:

• https://github.com/glyph/automat/blob/master/setup.py#L55
• https://github.com/glyph/automat/blob/master/tox.ini#L2

By the way, here's the pip installs for automat from PyPI for May 2018:

python_version	percent	download_count
2.7	57.26%	100,491
3.6	24.31%	42,663
3.5	16.10%	28,255
3.4	1.93%	3,385
3.7	0.40%	697
2.6	0.01%	12
3.3	0.00%	8
3.2	0.00%	2
Total		175,513

Source: pypinfo --start-date 2018-05-01 --end-date 2018-05-31 --percent --markdown automat pyversion

[glyph]

@hugovk Sure. Do you want to do another PR? :)

[hugovk]

Please see #103 :)