FEATURE: add graph support to admin reports

thanks to graph js, this runs latest beta cause we needed support for
smarter X axis legend

app/assets/javascripts/admin/components/admin-graph.js.es6

@@ -0,0 +1,43 @@
+import loadScript from 'discourse/lib/load-script';
+
+export default Ember.Component.extend({
+  tagName: 'canvas',
+
+  refreshChart(){
+    const ctx = this.$()[0].getContext("2d");
+    const model = this.get("model");
+    const rawData = this.get("model.data");
+
+    var data = {
+      labels: rawData.map(r => r.x),
+      datasets: [{
+        data: rawData.map(r => r.y),
+        label: model.get('title'),
+        backgroundColor: "rgba(200,220,240,0.3)",
+        borderColor: "#08C"
+      }]
+    };
+
+    const config = {
+      type: 'line',
+      data: data,
+      options: {
+        responsive: true,
+        scales: {
+          yAxes: [{
+            display: true,
+            ticks: {
+              suggestedMin: 0
+            }
+          }]
+        }
+      },
+    };
+
+    this._chart = new Chart(ctx, config);
+  },
+
+  didInsertElement(){
+    loadScript("/javascripts/Chart.min.js").then(() => this.refreshChart.apply(this));
+  }
+})