Fix version of Chart.js to 2.3 for now to due to breaking change for doughnut and polar area charts aspect ratio

Author: jtblin

package.json

@@ -65,6 +65,6 @@
   },
   "dependencies": {
     "angular": "1.x",
-    "chart.js": "2.x"
+    "chart.js": "2.3.x"
   }
 }