Added example, added makefile

gy521example.c

@@ -0,0 +1,14 @@
+#include <stdio.h>
+#include <wiringPi.h>
+#include "libgy521.h"
+
+int main(void) {
+    wiringPiSetup();
+    
+    setupgy521();
+    
+    while (1) {
+        printf("AngleX = %f, AngleY = %f, AngleZ = %f\n", getAngleX(), getAngleY(), getAngleZ());
+        delay(100);
+    }
+}