fix for latest Closure Compiler

The JSSourceFile class from the closure compiler was renamed, asset minification with v20141120 fails with
java.lang.ClassNotFoundException: com.google.javascript.jscomp.JSSourceFile

this commit updates the closure compiler dependency, bumps the version to
0.1.5-SNAPSHOT, and renames s/JSSourceFile/SourceFile/g

See https://github.com/clojure/clojurescript/commit/a4f7a89a887c483722f6ec6d75e0e7c76c7d92b2 for the same issue being fixed in Clojurescript