Class constructor. Input parameters specify the state of each output of the Pulse Streamer. Digital and analog output values are specified differently. In order to set a HIGH level at the digital channel, add the channel number to the channels list, for example channels=[0,2,3] will set HIGH level on the channels 0, 2 and 3. All other digital channels will be set to LOW. Output values at each of two analog outputs are specified with corresponding parameters A0 and A1.