Add tests for Solr/ES spatial order_by

This exists primarily to avoid the possibility of breaking
compatibility with the inconsistent lat, lon ordering used
by Django, Solr and ElasticSearch.

Travis: Enable IRC notifications

Mark 2.2.X as incompatible with Django 1.7

Release v2.2.0

Bumped to v2.1.0!

Bumped to v2.0.0!

Bumped to v1.2.7!

I hate Python packaging.

Avoid behaviour change by raising Http404 for invalid page numbers

An earlier version of this branch would always display the first page in this
case. For compatibility we now simply return 404.