Add OSX build to .travis.yml.  Clean up .travis.yml (#2689)
Add OSX build to .travis.yml.  Clean up .travis.yml (#2689)

* Add OSX build to .travis.yml.  Clean up .travis.yml
* Add gcc/gfortran to the mac brew setup.

iulian787/spack,EmreAtes/spack,mfherbst/spack,lgarren/spack,lgarren/spack,skosukhin/spack,mfherbst/spack,LLNL/spack,iulian787/spack,TheTimmy/spack,TheTimmy/spack,matthiasdiener/spack,skosukhin/spack,matthiasdiener/spack,tmerrick1/spack,tmerrick1/spack,iulian787/spack,skosukhin/spack,LLNL/spack,lgarren/spack,EmreAtes/spack,mfherbst/spack,matthiasdiener/spack,skosukhin/spack,matthiasdiener/spack,iulian787/spack,tmerrick1/spack,lgarren/spack,mfherbst/spack,lgarren/spack,tmerrick1/spack,krafczyk/spack,krafczyk/spack,EmreAtes/spack,EmreAtes/spack,LLNL/spack,krafczyk/spack,matthiasdiener/spack,krafczyk/spack,LLNL/spack,iulian787/spack,TheTimmy/spack,EmreAtes/spack,TheTimmy/spack,mfherbst/spack,skosukhin/spack,TheTimmy/spack,LLNL/spack,tmerrick1/spack,krafczyk/spack