Add example of GPS Sync feature

examples/TimeGPSSync/TimeGPSSync.ino

@@ -0,0 +1,40 @@
+#include <Time.h>
+#include <TinyGPS++.h>
+#include <SoftwareSerial.h>
+
+SoftwareSerial gps(3, 4); // RX, TX
+TinyGPSPlus gpsEncoder;
+
+void setup() {
+  Serial.begin(9600);
+  gps.begin(9600);
+
+  setSyncProvider(&gpsTimeSync);
+  setSyncInterval(5); // Seconds between re-sync
+}
+
+void loop() {
+  while (gps.available() > 0) {
+    gpsEncoder.encode(gps.read());
+  }
+  Serial.print("Now: ");
+  Serial.println(now());
+  delay(1000);
+}
+
+/**
+ * This is the magic, we get the date/time from the GPS unit
+ * and use it to convert to a time_t
+ */
+time_t gpsTimeSync(void) {
+  tmElements_t tm;
+
+  tm.Second = gpsEncoder.time.second();
+  tm.Minute = gpsEncoder.time.minute();
+  tm.Hour = gpsEncoder.time.hour();
+  tm.Day = gpsEncoder.date.day();
+  tm.Month = gpsEncoder.date.month();
+  tm.Year = CalendarYrToTm(gpsEncoder.date.year());
+
+  return makeTime(tm);
+}