simplify babelrc

.babelrc

@@ -1,10 +1,3 @@
 {
-  "env": {
-    "development": {
-      "presets": ["es2015", "stage-2"]
-    },
-    "production": {
-      "presets": ["es2015-rollup"]
-    }
-  }
+  "presets": ["es2015", "stage-2"]
 }