Merge pull request #4535 from guardian/jsh/target-es6

Target ES6

Author: jonathonherbert

kahuna/tsconfig.json

@@ -2,7 +2,7 @@
   "compilerOptions": {
     "noImplicitAny": true,
     "module": "es6",
-    "target": "es5",
+    "target": "es6",
     "lib": ["es6", "dom"],
     "jsx": "react",
     "alwaysStrict": true,