Add photos to quad in/out object documentation

gui/index.html

 	<p>Receive 16 bit quad (4) channel audio from two
 	<a href="http://www.pjrc.com/store/teensy3_audio.html" target="_blank">audio shields</a>
 		or another I2S devices, using I2S master mode.</p>
+	<p align=center><img src="img/audioshield_quad_in.jpg"></p>
 	</div>
 	<h3>Audio Connections</h3>
 	<table class=doc align=center cellpadding=3>
 	<h3>Summary</h3>
 	<div class=tooltipinfo>
 	<p>Transmit quad (4) channel 16 bit audio, using I2S master mode.</p>
+	<p align=center><img src="img/audioshield_quad_out.jpg"></p>
 	</div>
 	<h3>Audio Connections</h3>
 	<table class=doc align=center cellpadding=3>