Use long option in examples.

I had a hard time to grasp this switch. This would have helped a little.
Updated badge URLs and the doc link
Merge pull request #608 from clemens-tolboom/patch-1

Use long option in examples.
Add Gitter link to README

[ci skip]
Adding --priority flag that does nothing
Handling undefined priority algorithms
Implemented Feature-level reverse prioritiser
Fixing whitespace
Moving prioritiser to a tagged definition
Adding random prioritiser
Documentation error