MANPAGE: describe how to unmount, and that default options are fine
MANPAGE: describe how to unmount, and that default options are fine

Feedback received during the recent Go user group. If you haven't
used FUSE before, you don't know how to unmount, and it was not
described in the man page!

As for the options, there are many, and new users are intimidated
by it. State clearly that defaults are fine.

rfjakob/gocryptfs,rfjakob/gocryptfs,rfjakob/gocryptfs,rfjakob/gocryptfs