added touch support

[BerniWittmann]

I noticed, that this lib doesn't support touch events. (e.g. it doesn't work on a tablet)

that's why I added a property touchwhich lets the user enable or disable touch support.

[egoist]

Didn't tablet respond to click event?

[BerniWittmann]

Not in this case.
Links etc. are clickable on a tablet without a problem, but onclick-outside was not working. Maybe it's because the click event was bound to document in document.addEventListener. But this is just a guess.

Feel free to test it, but I can assure, that it was not working before on tablet and afterwards it does

[egoist]

I just came across kentor/react-click-outside#4 and they seem to leave this to userland

[BerniWittmann]

hmh.. also not a nice solution, but okay..
feel free to close, but maybe adding a small note in README (like they did) would be good

[egoist]

thanks, done.