Add the sniff make target

We can now run make sniff and this will provide correct command line arguments for all supported devices.

examples/sensniff/Makefile

@@ -23,3 +23,23 @@ all: $(CONTIKI_PROJECT)
 
 CONTIKI = ../..
 include $(CONTIKI)/Makefile.include
+
+PYTHON ?= python
+SENSNIFF = $(CONTIKI)/tools/sensniff/sensniff.py
+
+ifeq ($(BAUDRATE),)
+  BAUDRATE = 460800
+endif
+
+SENSNIFF_FLAGS += -b $(BAUDRATE)
+
+ifneq ($(PORT),)
+  SENSNIFF_FLAGS += -d $(PORT)
+endif
+
+sniff:
+ifeq ($(wildcard $(SENSNIFF)), )
+	$(error Could not find the sensniff script. Did you run 'git submodule update --init' ?")
+else
+	$(PYTHON) $(SENSNIFF) $(SENSNIFF_FLAGS)
+endif