[docs] Quick message - This link is broken

[anna at whoishostingthismail.com]

Hi,

I've been compiling resources to include in our guide to MPI and I came 
across a link that isn't working on your site.

It's on this page: http://pyacts.sourceforge.net/

I'm getting an error message when I visit this link: 
http://www-unix.mcs.anl.gov/mpi/mpich/

If you are planning on updating this page on your site, perhaps our 
guide to MPI -  http://wiht.link/MPIguide would make a suitable 
replacement.

Anna