Compile ONELAB on the Mac

ONELAB is an interface to finite element software, i.e., Gmsh and GetDP, for engineering applications. Homebrew science has been updated such that you can easily compile your own build on the Mac (after having installed brew):

> brew tap homebrew/science
> brew install gmsh --HEAD --with-fltk --with-petsc --with-slepc --with-opencascade
> brew install getdp --HEAD --with-petsc --with-slepc