Update README

Author: mbostock

README.md

@@ -274,7 +274,7 @@ Plot automatically generates axes for position scales. You can configure these a
 * *scale*.**ticks** - the approximate number of ticks to generate
 * *scale*.**tickSize** - the size of each tick (in pixels; default 6)
 * *scale*.**tickPadding** - the separation between the tick and its label (in pixels; default 3)
-* *scale*.**tickFormat** - to format tick values, either a function or a [d3-format](https://github.com/d3/d3-format#locale_format) or [d3-time-format](https://github.com/d3/d3-time-format#locale_format) specifier string; see [Formats](#formats)
+* *scale*.**tickFormat** - to format tick values, either a function or format specifier string; see [Formats](#formats)
 * *scale*.**tickRotate** - whether to rotate tick labels (an angle in degrees clockwise; default 0)
 * *scale*.**grid** - if true, draw grid lines across the plot for each tick
 * *scale*.**line** - if true, draw the axis line
@@ -1849,7 +1849,7 @@ The tension option only has an effect on cardinal and Catmull–Rom splines (*ca
 
 ## Formats
 
-These helper functions are provided for use as a *scale*.tickFormat [axis option](#position-options), as the text option for [Plot.text](#plottextdata-options), or for general use. See also [d3-time-format](https://github.com/d3/d3-time-format) and JavaScript’s built-in [date formatting](https://observablehq.com/@mbostock/date-formatting) and [number formatting](https://observablehq.com/@mbostock/number-formatting).
+These helper functions are provided for use as a *scale*.tickFormat [axis option](#position-options), as the text option for [Plot.text](#plottextdata-options), or for general use. See also [d3-format](https://github.com/d3/d3-format), [d3-time-format](https://github.com/d3/d3-time-format), and JavaScript’s built-in [date formatting](https://observablehq.com/@mbostock/date-formatting) and [number formatting](https://observablehq.com/@mbostock/number-formatting).
 
 #### Plot.formatIsoDate(*date*)