Remove Babel plugin for ES Modules (#2975)

* Remove Babel plugin for ES Modules

Processing of ES Modules is executed by Webpack.
Don't have to do it on Babel side.

* Add plugin for test

.babelrc

@@ -5,6 +5,7 @@
       "env",
       {
         "loose": true,
+        "modules": false,
         "targets": {
           "browsers": ["last 2 versions", "IE >= 11", "iOS >= 9"]
         }
@@ -33,6 +34,11 @@
       "plugins": [
         "lodash"
       ]
+    },
+    "test": {
+      "plugins": [
+        "transform-es2015-modules-commonjs"
+      ]
     }
   }
 }