docs(doc): Update default options description

Valentin Hervieu · Valentin Hervieu · commit ab2afaa1c942 · 2015-12-23T19:59:35.000+01:00
diff --git a/README.md b/README.md
@@ -167,6 +167,7 @@ The default options are:
     interval: 350,
     showTicks: false,
     showTicksValues: false,
+    ticksTooltip: null,
     ticksValuesTooltip: null,
     vertical: false,
     selectionBarColor: null,
