I think BuildHive (https://buildhive.cloudbees.com/) supports Pull Requests too. I'm using for my repositories, and I have an internal Jenkins server for private repositories.
Kohsuke Kawaguchi (the creator of Jenkins) has added this API to his Java library for Github: https://github.com/kohsuke/github-api/commit/892d2acaa2ca737... So, it's just a matter of time until that trickles downstream to the plugin and BuildHive.