allow test script to be found on the classpath rather than only looking for files

Diff is kind of messy, but the only change is wrapping the current if/else block in a if (!isClasspathResource(testScript)) statement.  This skips the file existence check if the path starts with a '@' (this will tell clojure.main where to find the file: http://clojuredocs.org/clojure_core/clojure.main/main).  

This would make it a lot easier for us to share a test script across all of our maven projects rather than copy-pasting it every time we change it.