URL validity testing + Travis CI integration

[klokan]

Create a set of tests on requests to the EPSG.io server - for the most critical URLs and the transform API - to prevent pull request breaking the essential functionality of the service.

It should be a set of request and tests of the expected results...

One of such examples recently broken is: http://epsg.io/21781-1753.js used in OpenLayers examples #103

[klokan]

A black box test against docker or latest running version could be configured on Travis.

Something similar was done for the iiifserver.

Config of Travis via .travis.yml: https://github.com/klokantech/iiifserver/blob/travis/.travis.yml The test itself is: https://github.com/klokantech/iiifserver/blob/travis/test.sh#L54