Squashed commit of the following:

commit 3c70032
Author: amacou <[email protected]>
Date:   Tue Jul 23 15:05:23 2019 +0900

    Fix getClasses function's filter works contrawise. Fixes Bttstrp#711

Author: izumiya

src/js/bootstrap-switch.js

@@ -12,7 +12,7 @@ function getClasses(options, id) {
     indeterminate ? 'indeterminate' : undefined,
     inverse ? 'inverse' : undefined,
     id ? `id-${id}` : undefined,
-  ].filter(v => v == null);
+  ].filter(v => v != null);
 }