Fix branch to 3.1 compatibility

.travis.yml

@@ -14,9 +14,9 @@ matrix:
     - php: 5.3
       env: DB=PGSQL CORE_RELEASE=3.1
     - php: 5.4
-      env: DB=MYSQL CORE_RELEASE=master
+      env: DB=MYSQL CORE_RELEASE=3.1
     - php: 5.5
-      env: DB=MYSQL CORE_RELEASE=master
+      env: DB=MYSQL CORE_RELEASE=3.1
 
 before_script:
  - phpenv rehash

composer.json

@@ -14,7 +14,7 @@
 	"require": {
 		"php": ">=5.3.2",
 		"composer/installers": "*",
-		"silverstripe/framework": "~3.1"
+		"silverstripe/framework": ">=3.1,<3.2"
 	},
 	"minimum-stability": "dev"
-	}
+}