Use uglify-js instead of uglify-js2

uglify-js2 is deprecated in favor of uglify-js@2.2.0

Author: oliversalzburg

package.json

@@ -34,7 +34,7 @@
         "karma-phantomjs-launcher": "^0.1.4",
         "karma-safari-launcher": "^0.1.1",
         "karma-sauce-launcher": "^0.2.10",
-        "uglify-js2": "^2.1.11"
+        "uglify-js": "^2.2.0"
     },
     "bugs": {
         "url": "https://github.com/stacktracejs/error-stack-parser/issues"