additional AnalogIn example

Revision:
0:490818b6238b
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Thu Jan 19 14:19:28 2017 -0600
@@ -0,0 +1,13 @@
+#include "mbed.h"
+
+AnalogIn position(A0);
+PwmOut servo(D3);
+
+int main() {
+    // servo requires a 20ms period    
+    servo.period(0.020f);
+    while (1) {
+        // servo position determined by a pulse width between 1-2ms
+        servo.pulsewidth(0.001f + 0.001f * position);
+    }
+}