README update

Add Opera 12- support description

Author: Sergey

README.md

@@ -38,6 +38,13 @@ We have to alter it a bit:
 ````
 That's it. It will work. But it **will not** work if you nest input inside label or put label before input.
 
+If you want to enable **Opera 12** and earlier support  just add class `styled` to `input` element:
+````
+...
+<input type="checkbox" id="checkbox1" style="styled">
+...
+````
+
 Radios
 ------------