[Travis] Simplify test matrix

Similar effort like ezsystems/ezpublish-legacy/pull/961

- As unit tests on 5.3.3 are broken, move it out and only care about
integration tests there until it and 5.3 is soon removed (RHEL7).
- Remove Solr 3.6, not interesting now that we got legacy upgraded
to Solr 4.x.
- Move TimeZone out of matrix to make it slightly more readable.
- Update to use solr 4.7.2, similar as used in ezfind.