Remove invalid combinations from travis config

* Ruby 1.9.2 does not work with Rails 4
* AA master does not work with Rails 3.1
* jruby and rbx do not work with current (development) dependencies
* Rails and AA master do not work together (via ransack and polyamorous)
* AA master does not require sass-rails
* sass-rails requires the asset pipeline to be explicitly enabled in Rails 3.1