Package for Bolt 1.4 added

I tested this package using a local repo as described [here](http://opam.ocamlpro.com/doc/Packaging.html#h1-TestingcustomOPAMpackages).

The ocamlfind META file still refers to the 1.3 version (as other files in the Bolt source distribution archive). I don't know whether I should add a patch to the opam package to change this. Anyway, I filed bug on the [Bolt bugtracker](http://bugs.x9c.fr/my_view_page.php).