Use es6, upgrade deps

package.json

@@ -53,17 +53,17 @@
     "start": "concurrently --kill-others -n Server,Typescript,Rollup 'npm run serve' 'tsc -w' 'rollup -c -w'"
   },
   "devDependencies": {
-    "@types/node": "^10.12.10",
+    "@types/node": "^10.12.12",
     "@types/json-stable-stringify": "^1.0.32",
     "browser-sync": "^2.26.3",
     "concurrently": "^4.1.0",
-    "prettier": "^1.15.2",
-    "rollup": "^0.67.3",
+    "prettier": "^1.15.3",
+    "rollup": "^0.67.4",
     "tslint": "^5.11.0",
-    "tslint-config-prettier": "^1.16.0",
-    "typescript": "^3.1.6",
-    "terser": "^3.10.12",
-    "vega-embed": "^3.24.2"
+    "tslint-config-prettier": "^1.17.0",
+    "typescript": "^3.2.1",
+    "terser": "^3.11.0",
+    "vega-embed": "^3.25.0"
   },
   "dependencies": {
     "vega-typings": "^0.3.51"

tsconfig.json

@@ -1,6 +1,6 @@
 {
   "compilerOptions": {
-    "target": "es5",
+    "target": "es6",
     "module": "es2015",
     "moduleResolution": "node",
     "declaration": true,