Add note to run all tests

Author: akoumjian

Makefile

@@ -1,7 +1,7 @@
 libassist: 
 	$(MAKE) -C src 
 	@ln -f -s src/libassist.so .
-	@if [ "$(MAKELEVEL)" -eq "0" ]; then echo "To compile the example problems, go to a subdirectory of examples/ and execute make there."; fi
+	@if [ "$(MAKELEVEL)" -eq "0" ]; then echo "To run tests, run 'make test' or go to a subdirectory of examples/ and execute make there."; fi
 
 all: libassist