Fix typo: Delete trailing colon in a couple headers.
Better match pattern for `entry`.
Reorganize some code.

- Move some IMAP-ish code from main.rkt to imap.rkt.
- Reorder main.rkt from top-level down.
Merge branch 'master' of github.com:greghendershott/feeds2gmail

* 'master' of github.com:greghendershott/feeds2gmail:
  Update README.md to describe `imap-append` situation.