Update README

Author: mbostock

README.md

@@ -233,7 +233,7 @@ const color = Plot.scale({color: {type: "linear"}});
 
 #### Scale objects
 
-Both [*plot*.scale](#plotscalescalename) and [Plot.scale](#plotscaleoptions) return scale objects. These objects represent the actual (or “materialized”) values encountered in the plot, including the domain, range, interpolate function, *etc.* The scale’s label, if any, is also returned; however, note that other axis properties are not currently exposed. Point and band scales also expose their materialized bandwidth and step.
+Both [*plot*.scale](#plotscalescalename) and [Plot.scale](#plotscaleoptions) return scale objects. These objects represent the actual (or “materialized”) scale options used by Plot, including the domain, range, interpolate function, *etc.* The scale’s label, if any, is also returned; however, note that other axis properties are not currently exposed. Point and band scales also expose their materialized bandwidth and step.
 
 To reuse a scale across plots, pass the corresponding scale object into another plot specification: