Add MPIDependency
Merge branch 'master' of github.com:scicalculator/homebrew-lammps

* 'master' of github.com:scicalculator/homebrew-lammps:
  Fix FFT_INC -I flag

Conflicts:
	lammps.rb
Rewrite caveats for more informative and understable reading
Improve python test
Radically improved package management

* Default packages can no longer be disabled
* options that select packages now use standard 'enable' sytax.
* Now only one option to install "all-standard" packages except those
  deamed "disabled. This has the benefit of radically simplifying
  installation of packages supported by sandia.
* Tested and ensured that most user contributed packages can be
  installed from options with the exception of cuda and atc with are
  trouble makers.
* Packages with additional libraries now properly make their libraries
  before-hand.
* Now use MPIDependency so that it does not select your mpi compiler for
  you. This allows you to choose for yourself if you want or use the
  apple provided compiler if you have an older machine. The downside is
  that there is a bug in homebrew at the moment which makes us depend on
  'scons' falsely because it sets up the environment for us correctly.
Add patch that fixes the lammps python module when homebrew is installed in a non-standard location