web: use object spread operator

While the spread operator is not part of ES6, React also uses it for JSX.
It makes sense for us to keep it in other parts of the codebase as well.

web/.babelrc

@@ -1,4 +1,4 @@
 {
   "presets": ["es2015", "react"],
-  "plugins": ["transform-class-properties"]
+  "plugins": ["transform-class-properties", "transform-object-rest-spread"]
 }

web/package.json

@@ -30,6 +30,7 @@
     "babel-core": "^6.7.7",
     "babel-jest": "^12.0.2",
     "babel-plugin-transform-class-properties": "^6.6.0",
+    "babel-plugin-transform-object-rest-spread": "^6.8.0",
     "babel-preset-es2015": "^6.6.0",
     "babel-preset-react": "^6.5.0",
     "babelify": "^7.3.0",