Add bechmark for rate and delta.

dist/datasource-zabbix/benchmarks/timeseries_bench.js

@@ -8,6 +8,8 @@ let series_set = [
   [[10.7104, 1498409636085], [10.578, 1498409651011], [10.5985, 1498409666628], [10.6877, 1498409681525], [10.5495, 1498409696586], [10.5981, 1498409711009], [10.5076, 1498409726949], [11.4807, 1498409741853], [11.6165, 1498409756165], [11.8575, 1498409771018], [11.9936, 1498409786056], [10.7566, 1498409801942], [10.7484, 1498409816010], [10.6038, 1498409831018], [10.2932, 1498409846010], [10.4912, 1498409861946], [10.4151, 1498409876871], [10.2401, 1498409891710], [10.4921, 1498409906143], [10.4413, 1498409921477], [10.6318, 1498409936147], [10.5277, 1498409951915], [10.6333, 1498409966052], [10.6417, 1498409981944], [10.4505, 1498409996867], [10.5812, 1498410011770], [10.4934, 1498410026573], [10.5731, 1498410041317], [10.5, 1498410056213], [10.6505, 1498410071013], [9.4035, 1498410086387]]
 ];
 
+let growing_series = [[10755200, 1498332216642], [10761200, 1498332276802], [10767200, 1498332336367], [10773200, 1498332396584], [10779200, 1498332456880], [10785200, 1498332516479], [10791200, 1498332576610], [10797200, 1498332636353], [10803200, 1498332696513], [10809200, 1498332756884], [10815200, 1498332816890], [10821200, 1498332876305], [10827200, 1498332936384], [10833200, 1498332996659], [10839200, 1498333056965], [10845200, 1498333116748], [10851200, 1498333176687], [10857200, 1498333236646], [10863200, 1498333297034], [10869200, 1498333356358], [10875200, 1498333416445], [4800, 1498333536686], [17900, 1498333667962], [24000, 1498333729157], [29500, 1498333783662], [34800, 1498333836813], [40700, 1498333896403], [46800, 1498333956953], [52800, 1498334016976], [6000, 1498334136593], [12000, 1498334196567]];
+
 module.exports = [
   {
     name: 'groupBy',
@@ -32,6 +34,17 @@ module.exports = [
       }
     }
   },
+  {
+    name: 'delta vs rate',
+    tests: {
+      'delta()': () => {
+        ts.delta(growing_series);
+      },
+      'rate()': () => {
+        ts.rate(growing_series);
+      }
+    }
+  },
   {
     name: 'groupBy vs groupBy_perf',
     tests: {