Using @Ocramius' highly opinionate renovate config

While it is not covered by a BC policy, @Ocramius is still maintaining
this stuff for now.

In the event that he no longer maintains this repo, this config should
be internalized in the @psr7-sessions organization instead.

renovate.json

@@ -1,6 +1,6 @@
 {
   "$schema": "https://docs.renovatebot.com/renovate-schema.json",
   "extends": [
-    "config:base"
+    "local>Ocramius/.github:renovate-config"
   ]
 }