Support some additional settings

I had some needs for additional settings, and am contributing back in case it's helpful.

* Allow overriding the cancel button text setting via `data-cancel`
* Add a class to the input text box with the `verifyClass` setting (i.e. in a bootstrap environment, I add `form-control` to inherit typical textbox settings)
* Add optional support for regular expression matching via `data-verify-regexp` and `data-verify-regexp-caseinsensitive`. The last one is really long, but perhaps not frequently used. This allows for scenarios like github's "delete repository" where you can type, for example, "data-confirm-modal" or "ifad/data-confirm-modal" to confirm.