Remove tests against symfony versions < 3.0

Author: DZunke

.travis.yml

@@ -21,10 +21,6 @@ matrix:
   fast_finish: true
 
 env:
-  - SYMFONY_VERSION="2.7.*" DECODA_VERSION="6.0.*"
-  - SYMFONY_VERSION="2.7.*" DECODA_VERSION="6.*"
-  - SYMFONY_VERSION="2.8.*" DECODA_VERSION="6.0.*"
-  - SYMFONY_VERSION="2.8.*" DECODA_VERSION="6.*"
   - SYMFONY_VERSION="3.0.*" DECODA_VERSION="6.0.*"
   - SYMFONY_VERSION="3.0.*" DECODA_VERSION="6.*"