Add Potentiometer example

examples/analog_io/potentiometer.rb

@@ -0,0 +1,14 @@
+#
+# Example for a potentiometer.
+#
+require 'bundler/setup'
+require 'denko'
+
+board = Denko::Board.new(Denko::Connection::Serial.new)
+pot = Denko::AnalogIO::Potentiometer.new(pin: :A0, board: board)
+
+pot.on_data do |reading|
+  puts "Potentiometer reading: #{reading}" if reading != pot.state
+end
+
+sleep