Cut down on MTT perl module requirements

Rainer mentioned that we're requiring a bunch of Perl modules that aren't necessarily installed by default on some older machines (e.g., his). He installed them to make it work, but it might be nice if we can cut down on the number of requirements -- particularly when running on MTT on parallel compute nodes, where perl installs are likely to be minimal (i.e,. all we need to do is run thests and dump output to files there; no need for fancy downloading perl modules, etc.). From a mail from Rainer:

It seems that quite a few packets are required to build the ParallelUserAgent-2.56:

libwww-perl-5.803 /* which is considered to be too new */
- depends on Compress-Zlib-2.000_05
URI-1.35
HTML-Parser
- depends on HTML-Tagset-3.10

open-mpi / mtt

Cut down on MTT perl module requirements #16