improve wording

README

@@ -180,7 +180,7 @@
  and
     http://w3.access.gpo.gov/bis/ear/pdf/740.pdf (EAR Section 740.13(e))
  for the details. If "your encryption source code is too large to serve as
- an email attachment", they are glad to receive a fax instead; hope you
+ an email attachment", they are glad to receive it by fax instead; hope you
  have a cheap long-distance plan.
 
  Our preferred format for changes is "diff -u" output. You might