Upgrade ring-core, ring-devel and ring-jetty-adapter from 1.4.0 => 1.7.1

[daveyarwood]

I'm working on a web app where we need to upgrade Jetty (and by extension, Ring) for security reasons. We use boot-http to serve the app locally for development, and we'd like to be able to use the same versions of Ring there.

I think ideally, there would be a way to specify what version of Ring you want to use, but in the absence of that, I think upgrading the default deps would be a good thing to do anyway.