Updates dependencies to ensure lockfile is not stale.

Author: weierophinney

composer.json

@@ -21,6 +21,7 @@
         "php": "^7.1",
         "ext-json": "*",
         "fig/http-message-util": "^1.1.2",
+        "http-interop/http-middleware": "^0.4.1",
         "psr/container": "^1.0",
         "psr/http-message": "^1.0",
         "spatie/array-to-xml": "^2.3",