Dropping python 3.5 support

[caspervdw]

Following up on #116

We decided that we want to start following numpy's deprecation protocol at https://numpy.org/neps/nep-0029-deprecation_policy.html .

For the next release, we want to limit Python to >= 3.6 and numpy to >= 1.15
GEOS we leave to >= 3.5 until Ubuntu 16 is out of support (April 2021).

@jorisvandenbossche will check with shapely what their policy is

[jorisvandenbossche]

All good on using Python 3.6+ here -> shapely/shapely#886

[jorisvandenbossche]

In the meantime Python 3.5 support has been removed (#211), and we have

pygeos/setup.py

Line 201 in b3ae300

python_requires=">=3.6",

So closing this issue.

[EwoutH]

@caspervdw is the aim still to follow Numpy's deprecation protocol NEP 29?

In that case Python 3.6 should be dropped, and preparations should take place to drop Python 3.7 support by Dec 26, 2021.

[caspervdw]

I agree, for the next release we should drop 3.6 (and also GEOS 3.6). Thanks for the heads up.