Add tests and add full URL helper.

[jezdez]

This also fixes Python 3 support and sets up running tox via Travis CI.

[jezdez]

@andrewgodwin A few questions:

• Should I add Codecov or something else to track test coverage?
• About the commit that adds nested URLs, I'd be interested what you think.
• I couldn't make sense of the callable checks in the string formatter (https://github.com/andrewgodwin/urlman/blob/8c3d40df893a621ce5bbe14fc44d37855e9f0d13/urlman/urls.py#L94-L96 and https://github.com/andrewgodwin/urlman/blob/8c3d40df893a621ce5bbe14fc44d37855e9f0d13/urlman/urls.py#L108-L109). Could you shed some light on the use case?

[andrewgodwin]

I haven't looked at this in two years, so it's taking a bit of remembering - bear with me!

• Code coverage is a good idea here I think, especially considering the small size

• The nested URL stuff looks OK, I think

• The callable checks are, I believe, so you can dispatch to other methods on the same model instance, and self gets correctly passed to them as they'd expect.

[jezdez]

@andrewgodwin So this is ready for another look. I've added code to enable Codecov on Travis-CI but you may need to go to Codecov actively and enable the repo there.

One thing I noticed is the non-existence of a license file. Which license do you want this to be published?

[andrewgodwin]

Lovely, thanks. I think it's ready to merge in if you're OK with that; I can add in the license file myself (I usually go with Apache 2, and see no reason to not keep doing that here)

[jezdez]

@andrewgodwin works for me!

[andrewgodwin]

Looks like the Travis builds worked for 2.7 and 3.4, but not 3.5 or 3.6, and I don't know why it can't find the python3.5 binary. Any idea? https://travis-ci.org/andrewgodwin/urlman/builds/223717184