Update to work with Guzzle v6

- upped php dependency to 5.5

README.md

@@ -29,7 +29,7 @@ Please try it out, and let me know if things are working as expected. There may
 
 All following examples assume this step.
 
-*Note:* The Hubspot class checks for a `HUBSPOT_API_KEY` environment variable if you don't include one during instantiation.
+*Note:* The HubSpot class checks for a `HUBSPOT_API_KEY` environment variable if you don't include one during instantiation.
 
 ```php
 $hubspot = Fungku\HubSpot\HubSpotService::make('api-key');

composer.json

@@ -10,16 +10,17 @@
         }
     ],
     "require": {
-        "php": ">=5.4.0",
-        "guzzlehttp/guzzle": "~5.0|~6.0"
+        "php": ">=5.5.0",
+        "guzzlehttp/guzzle": "~6.0"
     },
     "require-dev": {
         "phpspec/phpspec": "~2.0"
     },
     "autoload": {
         "psr-4": {
             "Fungku\\HubSpot\\": "src/"
-        }
+        },
+        "files": ["src/helpers.php"]
     },
     "minimum-stability": "stable"
 }