deal.II 8.2 (new formula)

Added support for deal.II library with numerous dependencies
and options.
well, it's just a way to say that deal.II could utilise boost if it is installed in Homebrew. The dependence is recommended. I think it makes sense to automatically install "boost" and link against it. Yet, i do not know any mechanism on how to enable it without "depends_on". Do you propose to make this dependence inside the "if...end" condition? Is it possible?