Don't format unrelated subfolders

Makefile

@@ -58,7 +58,7 @@ hooks:
 	echo "make fmt" >>.git/hooks/pre-commit
 
 fmt:
-	raco fmt -i $(shell find . -name '*.rkt')
+	@raco fmt -i $(shell find egg-herbie/ src/ infra/ -name '*.rkt')
 
 # This rule is run by herbie.uwplse.org on every commit to Github.
 # It does not restart the demo server, but it does pull new static content