[firedrake] Important info about keeping Firedrake up-to-date

Dear Firedrakers Next Friday (5 December), Firedrake's kernel optimisation system, COFFEE, will be moved into a separate repository. Past this date, if you wish to have an up-to-date Firedrake install you'll need to install one additional package (COFFEE) and update both PyOP2 and Firedrake. Installation instructions on the Firedrake web site will be updated at the same time, so following the instructions then will work. For the impatient, if you've followed the "pip install" instructions for previous installs, you will just need to run: sudo pip install git+https://github.com/coneoproject/COFFEE.git#egg=coffee -- Fabio