Adds support for python 3.6 in Code Climate

[chrishulton]

Changes

• Updates codeclimate-radon to not refer to specific python3.x version
• Will effectively bump python from 3.5.2 to 3.6.1 when incorporated in Code Climate

Details

This should address the string interpolation issue here: #108

Alpine edge now uses python version3.6.1 for the python3 package.
Since the Dockerfile builds from alpine:edge, just rebuilding the docker image will update python to 3.6.1:

(16/16) Installing python3 (3.6.1-r2)

However codeclimate-radon has an explicit reference to python3.5, which doesn't work after the update. I replaced it with the symlinked python3 rather than python3.6 which should be more flexible going forward.

If this looks good, when it's merged I will update Code Climate to reference the commit sha on master. This will incorporate the commits following our last update so it will bring us up to v1.5.0 (plus the few more recent commits).

[coveralls]

Coverage increased (+0.9%) to 99.284% when pulling 0c3fd65 on chrishulton:cc-bump-python-3.6 into b73c279 on rubik:master.

[rubik]

Thanks a lot for the details as well! 👍