fix echo which included unescape parens..

Makefile

@@ -9,4 +9,4 @@ deploy:
 update-tufte-css:
 	git subtree pull -P tufte-css --squash https://github.com/edwardtufte/tufte-css.git gh-pages
 	cp -Rp tufte-css/{tufte.css,et-book} content/media/css
-	@echo Make sure to git add content/media/css and commit the updates (if any)!
+	@echo 'Make sure to git add content/media/css and commit the updates (if any)!'