Update psr/http-message dependency to 1.0

Author: akrabat

composer.json

@@ -15,7 +15,7 @@
     "require": {
         "php": ">=5.4.0",
         "pimple/pimple": "~3.0",
-        "psr/http-message": "~0.9"
+        "psr/http-message": "^1.0"
     },
     "require-dev": {
         "slim/slim": "dev-develop"