Disabled buttons on Preview

Fixes [Issue
#82](https://github.com/toopay/bootstrap-markdown/issues/82)
Revert "Disabled buttons on Preview"

This reverts commit caf303a9f741b2d082336ee0a79679ac1c3581bc.
Revert "Revert "Disabled buttons on Preview""

This reverts commit ae97880e9ba65e5cb318231a653e5441e266c9f4.