0.3.1

This release is meant to fix the longstanding error some people have experienced in the REPL and build panes in which the main class could not be found (thank you to Reddit user /u/plewt). If anyone still gets the error, let me know and I'll see what I can do.

Additionally, this release improves the build behavior for pure Java projects so the build buttons are correctly enabled/disabled and the console prints output more reliably. Lastly, it updates play-clj to the latest version in the Clojure game template.