Improve the install target.

Makefile

@@ -89,8 +89,9 @@ run:
 	@ clear; ./$(EXE)
 
 install:
-	chmod u+s ./$(EXE)
-	mv ./$(EXE) /usr/local/bin
+	@ [ "$$(id -u)" = "0" ] && \
+	chmod u+s ./$(EXE)      && \
+	cp ./$(EXE) /usr/local/bin
 
 clean:
 	@ rm -rf $(EXE) $(EXE).dSYM