Justin B Rye pointed out (in Debian bug #566282) that a user with mail
in mbox format can spend a lot of time investigating notmuch before
realizing that mbox is not supported. Head that off with a more
detailed mention in the README blurb.
As Keith pointed out, (with a humorous citation from Mark Twain),
the two uses of "very" added nothing to the description. Also,
"large collection of email" was repeated uselessly.
