Add GalSim 1.0: a galaxy simulation toolkit, and dependency tmv-cpp, template matrix-vector library

GalSim is a package for simulating astronomical images of galaxies.
It was developed to support the upcoming "Great3" challenge,
http://great3challenge.info/, to test different methods for measuring
weak gravitational lensing, a key way of measuring mass in the
universe through its bending of light.

With the Great3 challenge set to begin soon, it would be great to have
GalSim in the main homebrew-science tap. I have been maintaining it in
our fork,
https://github.com/camphogg/homebrew-science/blob/master/gal-sim.rb
for several monhts. Probably 98% of professional astronomers use Mac
laptops, so it would be great to have gal-sim in the mainline
homebrew-science tap.

I am not a GalSim developer, though I do share an office with one.

tmv-cpp, a C++ templated matrix-vector math library, is a dependency
developed by one of the core gal-sim developers.
  http://code.google.com/p/tmv-cpp/