No Error Version of SignalHandle

[xvrqt]

Allow users to request a no error version of SignalHandle so they don't have to try!() each method call.
There's only one error at the moment and there's no way to recover and it's unlikely that sending messages fails if something else isn't seriously wrong.

This will make it more ergonomic for the majority of users.

addy::mediate(SIGINT).register("", || {}).enable();