Upgrade Bublé, use namedFunctionExpressions option

package.json

@@ -19,7 +19,7 @@
     "node-static": "0.6.0",
     "phantomjs-prebuilt": "^2.1.12",
     "rollup": "^0.34.10",
-    "rollup-plugin-buble": "^0.14.0",
+    "rollup-plugin-buble": "^0.15.0",
     "rollup-watch": "^2.5.0"
   },
   "bugs": "http://github.com/codemirror/CodeMirror/issues",

rollup.config.js

@@ -14,5 +14,5 @@ export default {
   format: "umd",
   dest: "lib/codemirror.js",
   moduleName: "CodeMirror",
-  plugins: [ buble() ]
+  plugins: [ buble({namedFunctionExpressions: false}) ]
 };