fix(package): update @webcomponents/webcomponentsjs to version 2.4.0

Closes #16

Author: greenkeeper[bot]

package.json

@@ -13,7 +13,7 @@
   "author": "Henri Bergius <[email protected]>",
   "license": "MIT",
   "dependencies": {
-    "@webcomponents/webcomponentsjs": "^1.0.19",
+    "@webcomponents/webcomponentsjs": "^2.4.0",
     "color-interpolate": "^1.0.2",
     "d3": "^4.12.0",
     "dateformat": "^3.0.2",