rearrange the "In summary" text so that it:
 - words it so the preferred choice is first in the sentence
 - talks about what it means for tlsa to not apply (defer delivery,
   etc)
mention that insecure is not "bogus"
minor wording changes
use a hanging list for CNAME vs Non-CNAME
MX fixes for cname/non-cname.  These paragraphs still need work