Update README.

Author: mbostock

README.md

@@ -247,11 +247,9 @@ Like [ES6 Maps](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Referenc
 * Keys are coerced to strings.
 * [map.set](#map_set) returns the new value, not the map itself.
 * [map.each](#map_each), not [map.forEach](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map/forEach). (Also, no *thisArg*.)
-* [map.remove](#map_remove), not [map.delete](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map/delete).
-* No [map.clear](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map/clear).
+* [map.remove](#map_remove), not [map.delete](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map/delete); also, no [map.clear](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map/clear).
 * [map.entries](#map_entries) returns an array of {key, value} objects, not an iterator of [key, value].
-* [map.size](#map_size) is a method, not a [property](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map/size).
-* A [map.empty](#map_empty) method.
+* [map.size](#map_size) is a method, not a [property](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map/size); also, there’s [map.empty](#map_empty).
 
 <a name="map" href="#map">#</a> <b>map</b>([<i>object</i>[, <i>key</i>]])
 
@@ -313,10 +311,8 @@ Like [ES6 Sets](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Referenc
 * Values are coerced to strings.
 * [set.add](#set_add) returns the new value, not the set itself.
 * [set.each](#set_each), not [set.forEach](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set/forEach). (Also, no *thisArg*.)
-* [set.remove](#set_remove), not [set.delete](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set/delete).
-* No [set.clear](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set/clear).
-* [set.size](#set_size) is a method, not a [property](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set/size).
-* A [set.empty](#set_empty) method.
+* [set.remove](#set_remove), not [set.delete](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set/delete); also, no [set.clear](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set/clear).
+* [set.size](#set_size) is a method, not a [property](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set/size); also, there’s [set.empty](#set_empty).
 
 <a name="set" href="#set">#</a> <b>set</b>([<i>array</i>])