psr/cache is not needed, do also test with sf2.6

Author: Nyholm

.travis.yml

@@ -5,6 +5,7 @@ php:
   - "5.5"
 
 env:
+  - SYMFONY_VERSION=2.6.*
   - SYMFONY_VERSION=2.7.*
   - SYMFONY_VERSION=2.8.*
   - SYMFONY_VERSION=3.0.*

composer.json

@@ -25,9 +25,8 @@
     ],
     "require":      {
         "php":                      "^5.5|^7",
-        "symfony/framework-bundle": "^2.7|^3.0",
-        "psr/cache-implementation": "~1.0",
-        "psr/cache":                "1.0.x-dev"
+        "symfony/framework-bundle": "^2.6|^3.0",
+        "psr/cache-implementation": "~1.0"
     },
     "require-dev":  {
         "phpunit/phpunit":        "^5.1|^4.0",