Don't handle key events if theres no modal open.

[abimaelmartell]

After opening (then closing) two modals at the same time, the TAB key stops working as expected.

swal('adsa'); swal('asdads');
// then click ok

This PR adds a check for a open modal before doing anything on the keydown event.

[abimaelmartell]

Should i include the generated changes from dist and lib? The gulp task did some changes there.

[Stichoza]

Does it fix #127?

[abimaelmartell]

yes