Allowing ProxyManager v2 installation

Author: Ocramius

composer.json

@@ -19,7 +19,7 @@
     },
     "require-dev": {
         "phpunit/phpunit": "~4.6",
-        "ocramius/proxy-manager": "~1.0",
+        "ocramius/proxy-manager": "^1.0 || ^2.0",
         "squizlabs/php_codesniffer": "^2.0@dev",
         "phpbench/phpbench": "^0.10.0"
     },