lammps 2013.05.14
lammps 2013.05.14

* update to latest version
* disable user-omp package
  - clang does not yet support OMP
  - This required gcc dependency greater than 42
    + previously gcc formula was latest version, but
      it is now versioned
    + tricky to maintain dependency on gcc when user
      can have any version installed.
    + easier to just disable it for now

pmelsted/homebrew-science,andrewjpage/homebrew-science,ahundt/homebrew-science,ge11232002/homebrew-science,goxberry/homebrew-science,maplesond/homebrew-science,kozo2/homebrew-science,joshbode/homebrew-science,philippbayer/homebrew-science,DabeDotCom/homebrew-science,heuermh/homebrew-science,dpo/homebrew-science,quantumsteve/homebrew-science,aeantipov/homebrew-science,parcollet/homebrew-science,pditommaso/homebrew-science