Add a Beep() method to the Screen interface. On *nix systems, this
writes the bell character (0x07) to the tty. On Windows, we call the
MessageBeep syscall.
Fixes: #2
We had problems where if $TERM was set on a Windows console, we would
fail to allocate the screen because of missing termios. This caused
lots of problems for many Windows users. This should make this easier
for folks who might have set $TERM for other reasons, even in a Windows
console environment.
Eventually we will want to support emitting characters for 256 color
support, but that's later.
fixes#38 Broke wide characters in last update
fixes#39 Clean up logic for encodings, enhance fallback options
fixes#36 Support more mouse buttons on Windows.
