allow charts to have Y-axis min and max specified

app/views/docs/charts.html.erb

@@ -33,6 +33,8 @@
       <li><b>dynamic</b> (true/false) Make chart update automatically every 15 seconds, default: false (optional)</li>
       <li><b>step</b> (true/false) Draw chart as a step chart, default: false (optional)</li>
       <li><b>export</b> (true/false) Show export buttons, so that chart can be saved as an image, default: false (optional)</li>
+      <li><b>yaxismin</b> (decimal) Minimum value of chart's Y-Axis; if blank the value is auto-calculated (optional)</li>
+      <li><b>yaxismax</b> (decimal) Maximum value of chart's Y-Axis; if blank the value is auto-calculated (optional)</li>
     </ul>
 
     <br>