[notmuch] [PATCH-v2] Don't eat last newline character of citations

[Kan-Ru Chen]

This patch series fixed the indentation problem of git HEAD and did
some minor cleanup of (- (..) 1) usage.

The second patch connects two citations block if them are blank line
separated, for example:

    > block 1
    > block 1

    > block 2

Will be treat as one citation block. The side effect is that any blank
line following the citation will be hidden, too.

The fourth patch is intend to decorate the citation button with
font-lock-comment-face so that the button can stand out form other
contents.

Cheers,
            Kanru