Cleanup Makefile - cache shunit2 files

Makefile

@@ -22,23 +22,26 @@ test_unit:
 	go test `glide novendor`
 	#go run tests/tendermint/*.go
 
-test_cli: get_shunit2
+test_cli: tests/cli/shunit2
 	# sudo apt-get install jq
 	@./tests/cli/basictx.sh
 	@./tests/cli/counter.sh
 	@./tests/cli/restart.sh
 	@./tests/cli/ibc.sh
 
-test_tutorial:
+test_tutorial: docs/guide/shunit2
 	shelldown ${TUTORIALS}
 	for script in docs/guide/*.sh ; do \
 		bash $$script ; \
 	done
 
-get_shunit2:
+tests/cli/shunit2:
 	wget "https://raw.githubusercontent.com/kward/shunit2/master/source/2.1/src/shunit2" \
     	-q -O tests/cli/shunit2
-	cp tests/cli/shunit2 docs/guide/shunit2
+
+docs/guide/shunit2:
+	wget "https://raw.githubusercontent.com/kward/shunit2/master/source/2.1/src/shunit2" \
+    	-q -O docs/guide/shunit2
 
 get_vendor_deps: tools
 	glide install