fixes now compiles

src/gps/UBloxGPS.h

@@ -2,7 +2,7 @@
 
 #include "GPS.h"
 #include "Observer.h"
-#include "PeriodicTask.h"
+#include "../concurrency/PeriodicTask.h"
 #include "SparkFun_Ublox_Arduino_Library.h"
 
 /**
@@ -10,7 +10,7 @@
  *
  * When new data is available it will notify observers.
  */
-class UBloxGPS : public GPS, public PeriodicTask
+class UBloxGPS : public GPS, public concurrency::PeriodicTask
 {
     SFE_UBLOX_GPS ublox;