COMP: Travis CI build should use single core 
COMP: Travis CI build should use single core 

Test if Travis VMs stalls because they run out of memory
kaspermarstal/SuperElastix,SuperElastix/SuperElastix,SuperElastix/SuperElastix,SuperElastix/SuperElastix,kaspermarstal/SuperElastix,SuperElastix/SuperElastix,kaspermarstal/SuperElastix