Merge pull request #181 from jgoldfar/patch-1

Update build script to fix Mac CI

Author: JaredCrean2

conf/travis-install-mpi.sh

@@ -12,7 +12,6 @@ case "$os" in
     Darwin)
         brew update
         brew upgrade cmake
-	    brew upgrade gcc
         case "$MPI_IMPL" in
             mpich|mpich3)
                 brew install mpich