use cl-lib library instead of cl library

Use `cl-loop' intead of `loop' and in one case remove the WITH clause
and instead wrap the `cl-loop' with `cl-destructuring-bind'.  It appears
that the `cl-lib' of Emacs v24.4 no longer supports destructuring in the
WITH clause.

Fixes issue #13.
locally unset indent-tabs-mode
Merge pull request #14 from tarsius/master

use cl-lib library instead of cl library