Include Immutant in the benchmarks

I tweaked the run-servers.sh script to lazily install immutant, deploy a simple ring app with the same behavior as the others, and run the server, listening for web requests on 8095.

I'm including a graph and a link to the supporting google spreadsheet. Obviously, my laptop is a tad underpowered, but the relative results show immutant about where I would expect: below the servlets and slightly above the jetty ring adapter.

I'm at a loss to explain my results for nginx-clojure, however. It appears I may have something misconfigured.