Fixing some of requested changes for pull request

readme.md

@@ -165,19 +165,36 @@ The wrapper marks the unprintable characters from style tags.
 A wrapper can be added to the styles, so you can escape characters or add marks to then.  
 By default, these wrappers are empty strings `""`.
 
-The wrappers object has two properties, `pre` and `post`.  
+The wrappers object has two properties, `before` and `after`.  
 For example:
 
 ```js
-const ctx = new chalk.constructor({wrapper: {
-	pre: '>',
-	post: '<',
-}});
+const ctx = new chalk.constructor({
+	wrapper: {
+		before: '>',
+		after: '<'
+	}
+});
 
-ctx.red('foo') // outputs "><foo><"
+ctx.red('foo') // outputs ">\u001B[31m<foo>\u001B[39m<"
 ```
 
-This can be specially useful when escaping characters, using it into a _PS1_ string or debugging and outputing it into different terminals/TTYs.
+This can be specially useful when escaping characters, using it into a _PS1_ string or debugging and outputing it into different terminals/TTYs.  
+That's because _PS1_ uses the number of _printable_ characters to know the length of the string and to position the cursor. If you don't mark the colour codes as "unprintable" by using `\[` and `\]`, those characteres will be used to determine the length of the string, mispositioning the cursor.
+
+```js
+const ctx = new chalk.constructor({
+	wrapper: {
+		before: '\\[',
+		after: '\\]'
+	}
+});
+
+ctx.red('foo') // outputs "\\[\u001B[31m\\]foo\\[\u001B[39m\\]" (marking the colour codes as unpritable)
+```
+
+That would output "foo" in red, as that is the printable result.
+
 
 ### chalk.supportsColor