tappet.in: Add to the repository

* tappet.in: Add to the repository.  The script can be used to push
  IRC logs into the web.  It has not been completed yet, though.
* Makefile.am (bin_SCRIPTS): Add the tappet.
  (EXTRA_DIST): Likewise.
  (SUFFIXES): Add `.in' suffix.
  (CLEANFILES): Add scripts.