Fix typos in Phaser.Group#forEachExists for docs phaserjs#447

Author: photonstorm

src/core/Group.js

@@ -817,11 +817,11 @@ Phaser.Group.prototype.forEach = function (callback, callbackContext, checkExist
 }
 
 /**
-* Allows you to call your own function on each alive member of this Group (where child.alive=true). You must pass the callback and context in which it will run.
+* Allows you to call your own function on each member of this Group where child.exists=true. You must pass the callback and context in which it will run.
 * You can add as many parameters as you like, which will all be passed to the callback along with the child.
-* For example: Group.forEachAlive(causeDamage, this, 500)
+* For example: Group.forEachExists(causeDamage, this, 500)
 * 
-* @method Phaser.Group#forEachAlive
+* @method Phaser.Group#forEachExists
 * @param {function} callback - The function that will be called. Each child of the Group will be passed to it as its first parameter.
 * @param {Object} callbackContext - The context in which the function should be called (usually 'this').
 */