Add tickDecimals to the setting-options example.

It's useful to include the tickDecimals option in one of our examples,
so it's easier to test across versions.  The setting-options example is
the logical place to put it.

examples/setting-options.html

@@ -48,7 +48,8 @@ $(function () {
         yaxis: {
             ticks: 10,
             min: -2,
-            max: 2
+            max: 2,
+            tickDecimals: 3
         },
         grid: {
             backgroundColor: { colors: ["#fff", "#eee"] }