Remove code for unsupported Python versions

[hugovk]

Follow on from #2822 and for #2812 and removes some other code for old unsupported versions.

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Here's a quick checklist that should be present in PRs:

• Add a new news fragment into the changelog folder
  • name it $issue_id.$type for example (588.bug)
  • if you don't have an issue_id change it to the pr id after creating the pr
  • ensure type is one of removal, feature, bugfix, vendor, doc or trivial
  • Make sure to use full sentences with correct case and punctuation, for example: "Fix issue with non-ascii contents in doctest text files."
• Target: for bugfix, vendor, doc or trivial fixes, target master; for removals or features target features;
• Make sure to include reasonable tests for your change if necessary

Unless your change is a trivial or a documentation fix (e.g., a typo or reword of a small section) please:

• Add yourself to AUTHORS;

[RonnyPfannschmidt]

good work running trough all the small details 👍

[hugovk]

Marking the news fragment as done, as there's already one in #2822:

remove support for the eol python versions 2.6 and 3.3

(This PR also removes some < (2,6) and < (2,5) :)

[coveralls]

Coverage increased (+0.06%) to 92.562% when pulling 7113c76 on hugovk:features-rm-2.6 into dd45f8b on pytest-dev:features.

[RonnyPfannschmidt]

well done, its really nice to have someone step in and sort out all the little tedious details 👍