Other exception sources

[seanhandley]

It'd be cool if it could go via a Rack middleware to get at exception text. That way it'd work on any rack-based application, e.g. Sinatra

[excid3]

I got thinking about that too recently. Definitely think it would be good to create a new branch and build a Rack middleware for the next version. I'd also love to integrate this with better_errors.