Changed install section of Makefile to work on Mac OS X (#213)

Makefile

@@ -290,11 +290,11 @@ $(BENCHMARK_BINS): build/benchmarks/%_benchmark: build/benchmarks/%.go $(RUNTIME
 
 install: $(RUNNER_BIN) $(COMPILER) $(RUNTIME) $(STDLIB)
 	# Binary executables
-	install -Dm755 build/bin/grumpc "$(DESTDIR)/usr/bin/grumpc"
-	install -Dm755 build/bin/grumprun "$(DESTDIR)/usr/bin/grumprun"
+	install -d "$(DESTDIR)/usr/bin"
+	install -m755 build/bin/grumpc "$(DESTDIR)/usr/bin/grumpc"
+	install -m755 build/bin/grumprun "$(DESTDIR)/usr/bin/grumprun"
 	# Python module
 	install -d "$(DESTDIR)"{/usr/lib/go,"$(PY_INSTALL_DIR)"}
-	cp -rv --no-preserve=ownership "$(PY_DIR)/grumpy" "$(DESTDIR)$(PY_INSTALL_DIR)"
+	cp -rv "$(PY_DIR)/grumpy" "$(DESTDIR)$(PY_INSTALL_DIR)"
 	# Go package and sources
-	cp -rv --no-preserve=ownership build/pkg build/src "$(DESTDIR)/usr/lib/go/"
-
+	cp -rv build/pkg build/src "$(DESTDIR)/usr/lib/go/"