BREAKING CHANGE: Rails 4 support. w:@lleirborras cc:@Thorsson :beer: (v0.7.0.alpha)

There is an API change, as now .history does NOT return sorted
records by default. Add .sorted to obtain the same result.

This UNFORTUNATELY re-introduces a CAVEAT, that is disabling
tsrange parsing on AR4 that it is currently broken. See the
README for more information.