Don't test Rack 1.4, since we won't use it.

Also don't test Rack master on 1.9.3, since they've dropped support.

.travis.yml

@@ -17,9 +17,7 @@ sudo: false
 
 matrix:
   include:
-    - { rvm: 1.9.3, env: rack=1.4.0  }
     - { rvm: 1.8.7, env: tilt=master }
-    - { rvm: 1.9.3, env: rack=master }
     - { rvm: 1.9.3, env: tilt=master }
     - { rvm: 2.2, env: rack=master }
     - { rvm: 2.2, env: tilt=master }