Remove the `mock` code path in Board's constructor. Allow disabling of debug mode.

The mock code path is not necessary with new 'isReady' io object flag. Without mock it is now desirable to allow disabling of debug mode. It still defaults to true.
When MockFirmata io plugin is used, don't bind process events in broadcast call

Signed-off-by: Rick Waldron <waldron.rick@gmail.com>