Merge pull request #8 from clovnrian/master

Update guzzlehttp/psr7 to the latest version

Author: nilportugues

composer.json

@@ -14,7 +14,7 @@
     ],
     "require": {
         "psr/http-message": "1.0.*",
-        "guzzlehttp/psr7": "1.2.*",
+        "guzzlehttp/psr7": "^1.3.1",
         "nilportugues/assert": "^1.0"
     },
     "require-dev": {