Remove Python 3.4

[kornicameister]

Fixes #977 .

Changes proposed in this pull request:

• remove Python 3.4 support
• upgrade Python version in docs
• remove backport import to HttpStatus

[kornicameister]

@hjacobs question still remain, should we drop old 2.7 as well ?
Dropping older python and starting with 3.5 would open up possibility to enhance codebase with mypy and typing which I could do :)

[kornicameister]

I believe pytest-dev/pytest#5532 contains reason for failure.

[kornicameister]

I've created an issue here: #991
I think that before any actions are taken, that ought be taken care of.

[kornicameister]

@hjacobs perhaps, if you have time, you can take a look at this one here.

[hjacobs]

Thanks!

[hjacobs]

👍

[kornicameister]

Ok, guess that means we stick with 2.7 for now 👍