Raise error if ruby 1.9.3 is detected.

@mperham, Let me know if i need to reformulate the error message.

I did it here to have an early error. For me both places are ok, i would like opinions of others.
ping @brandonhilkert , @jonhyman , @ryanlecompte , @jc00ke ...

Rubinius and others don't work because of the unicode heart anyway. And even if when they do rbx-edge, their ruby version is over 2.0.0+