Revert "Use puppet-mode in Emacs"

This reverts commit b25070667bea46eb113ece8486e9cf23502eeb9b.

This is somehow breaking Emacs intialization with "wrong number of
arguments".
Add Mozilla-style .hgrc
Use emacs24 for sensible-editor

With the installation of a backported emacs24 package onto
steevie, Emacs 24 is now available on all the Debian systems I
regularly use. Additionally, the previous selection (emacs23) was
causing issues on installations of Sid.

Therefore, select Emacs 24 as the default editor for
sensible-editor.
Apparently #foxymonkeys is dead :(

It's the end of an era... so many QDB quotes, cruelly
decontextualized. Sadness forever.