Added provide for php-http/message-factory-implementation, fixes #75 (#80)

Author: Nyholm

composer.json

@@ -16,6 +16,9 @@
         "php-http/message-factory": "^1.0.2",
         "clue/stream-filter": "^1.3"
     },
+    "provide": {
+        "php-http/message-factory-implementation": "1.0"
+    },
     "require-dev": {
         "zendframework/zend-diactoros": "^1.0",
         "guzzlehttp/psr7": "^1.0",