Mobile friendly host by default

Fixes #37 so you no longer need to set the host on windows.
Adds functionality from #52  
Note that the mobile friendly address and `localhost:4567` both work with LiveReload simultaneously so it shouldn't cause any backward-compatability problems.

It doesn't yet print the IP where LiveReload is running, I could just put:
`logger.info "== Livereload is connecting to http://#{host}:4567 (localhost)"`
at the top of the ready block, not sure if that's the right place to put it though.

Not tested on Linux!