Remove factories from discovery

Author: sagikazarmark

composer.json

@@ -19,15 +19,15 @@
         "php-http/message-factory": "^1.0"
     },
     "require-dev": {
+        "php-http/utils": "dev-factories",
         "zendframework/zend-diactoros": "^1.0",
         "guzzlehttp/psr7": "^1.0",
         "php-http/guzzle6-adapter": "^0.2",
         "phpspec/phpspec": "^2.4",
         "henrikbjorn/phpspec-code-coverage" : "^1.0"
     },
     "suggest": {
-        "zendframework/zend-diactoros": "Used with Diactoros Factories",
-        "guzzlehttp/psr7": "Used with Guzzle PSR-7 Factories"
+        "php-http/utils": "To use Message Factories"
     },
     "autoload": {
         "psr-4": {