Y-axis labels for min and max

Hi there,

loving the library! Just wondering if it is possible somehow to show the min and max values of the y-Axis to show the scaling of the sparkline.

I.e. right now, if your data changes by 0.01 the sparkline will draw a major spike, and the user doesn't know how big the increase is. If we had Y-axis labels they could get an idea.

Any thoughts on how to do this?