Fixed sections regarding validations and callbacks to mention the tou…

…ch method does not fire either validations or callbacks as stated in the docs.

railties/guides/source/active_record_validations_callbacks.textile

@@ -82,6 +82,7 @@ The following methods skip validations, and will save the object to the database
 * +increment!+
 * +increment_counter+
 * +toggle!+
+* +touch+
 * +update_all+
 * +update_attribute+
 * +update_column+
@@ -1007,6 +1008,7 @@ Just as with validations, it's also possible to skip callbacks. These methods sh
 * +increment+
 * +increment_counter+
 * +toggle+
+* +touch+
 * +update_column+
 * +update_all+
 * +update_counters+