Support automatic dependency update checking

[pwhittin]

I just added support for automatic dependency update checking via Depot.

To do so I added Depot to my bin/app project's deps.edn file. Additionally, I added a new script in bin named 'outdated' using the 'clojure' execution line suggested by the Depot docs.

There are two things that would be nice to have:

1. Integrate this into Edge (i.e., Add an :outdated alias to 'bin/app' generated deps.edn, and add a 'bin/outdated' script.
2. Create and maintain some sort of Maven/Clojars/etc. artifact that tracked Edge's current version so that Depot would report that a new Edge version is available.

[SevereOverfl0w]

I don't think I would create an alias in the default deps.edn, but a bin script for checking outdated deps would be useful.

I'm not sure how to do the Edge check, might be able to do something with git fetch followed by git log HEAD...FETCH_HEAD.