Fixed versionnumber

Author: Martin

README.md

@@ -13,7 +13,7 @@ to your `composer.json` file:
 ```json
 {
     "require": {
-        "cardgate/omnipay-cardgate": "~1.0"
+        "cardgate/omnipay-cardgate": "~2.0"
     }
 }
 ```

composer.json

@@ -31,7 +31,7 @@
     },
     "extra": {
         "branch-alias": {
-            "dev-master": "1.0.x-dev"
+            "dev-master": "2.0.x-dev"
         }
     }
 }