[UPDATE] README.

README.md

@@ -36,7 +36,7 @@ var str = '[<start>:<stop>:<increment>]';
 ```
 
 Notes about the notation:
-* 	If an `increment` is not specified, the default increment is `1`. An `increment` cannot be set to zero.
+* 	If an `increment` is not specified, the default increment is `1`. An `increment` of zero is __not__ allowed.
 *	The `start` index is __inclusive__, while the `stop` index is __exclusive__.
 * 	Both `start` and `stop` indices are *optional*. If not provided, `start` and `stop` default to index extremes.
 * 	Both `start` and `stop` can be negative, in which case they specify the number of indices from the __end__ of an `array`.