fix(checkbox/radio): fix issue #49 for default custom radio groups

Author: Lausselloic

app/less/o-buttons.less

@@ -681,7 +681,7 @@
   border: 2px solid #000;
 
   .btn {
-    width: @toggles-3-way-width;
+    min-width: @toggles-3-way-width;
     padding-right: 0;
     padding-left: 0;
     margin: 0;