Multiple frames (#8)

* Add fields to mmr header

* Reorder priority constants

* Add message priority

* Add header to message

* Fix compile error

* Set correct bits in header

* Refactor

* Create queue

Inc/mmr_can_queue.h

@@ -0,0 +1,14 @@
+#ifndef INC_MMR_CAN_QUEUE_H_
+#define INC_MMR_CAN_QUEUE_H_
+
+#include <stdint.h>
+#include "mmr_can.h"
+
+#define MMR_CAN_QUEUE_SIZE 10
+
+typedef struct {
+  MmrCanMessage messages[MMR_CAN_QUEUE_SIZE];
+  size_t count;
+} MmrCanQueue;
+
+#endif /* INC_MMR_CAN_QUEUE_H_ */