Added support for Internet Explorer 11.

Thanks to Ales Hladilek for the contribution.
Clean up demo
Increase version number.
Corrected unprefixed W3C method/property names (Closes: #13)
Stop using ALLOW_KEYBOARD_INPUT.

In Chrome it no longer makes a difference and in Safari it doesn't help
anyway (Fullscreen forms are always read-only). In older Safari the code
didn't work at all so I hope this is now better.
Created new minimized version.
Mention IE11 and add a known issues section.