Try to fix CI problems

[megies]

..and also update install docs.

• rest framework dropped django 1.9 compat with 3.7.0
• there's a problem with django parsing geos version. not sure if it's due to conda changing the version number in packaging (then this fix is appropriate) or if the version scheme in geos has changed with newer versions (then another option would be to limit geos version number in Travis

[megies]

I think these fixes work but looks like there's also some docs building issue and also one test is failing not sure why.

[megies]

@krischer what's the reasoning behind this one? a58e8052d110ca4ae0284e2767bfb55f060ea6ae

It's failing a test that is explicitly using an empty network string (the test data also has an empty network.

[megies]

If there's no objections I'm gonna merge this one. Pretty sure that test fails are unrelated and master branch is failing CI anyway.