fixed Casper.each() wasn't logging ertror properly

@@ -301,7 +301,7 @@
          */
         each: function(array, fn) {
             if (!isType(array, "array")) {
-                self.log("each() only works with arrays", "error");
+                this.log("each() only works with arrays", "error");
                 return this;
             }
             (function(self) {