Merge pull request #7 from ghostwriter/feature/http-message-v2

Support `psr/http-message` v2

Author: Jean85

composer.json

@@ -21,7 +21,7 @@
     ],
     "require": {
         "php": ">=7.0",
-        "psr/http-message": "^1.0"
+        "psr/http-message": "^1.0 || ^2.0"
     },
     "autoload": {
         "psr-4": {