TravisCI: Try re-activating OSX build
TravisCI: Try re-activating OSX build

Based on Travis customer support message: Additional details for each OS (e.g. requesting sudo-less Trusty container) can only appear in the matrix - include section, not in the OS section.

MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3,MRtrix3/mrtrix3