limit processors to use in Travis build to 4
limit processors to use in Travis build to 4

antidotcb/googletest,jlanecox/googletest,fuchsia-mirror/third_party-googletest,antidotcb/googletest,gianricardo/googletest,antidotcb/googletest,xnagireddy/googletest,gianricardo/googletest,xnagireddy/googletest,fuchsia-mirror/third_party-googletest,google/googletest,fuchsia-mirror/third_party-googletest,antidotcb/googletest,empiredan/googletest,google/googletest,fuchsia-mirror/third_party-googletest,google/googletest,jlanecox/googletest,jlanecox/googletest,empiredan/googletest,xnagireddy/googletest,gianricardo/googletest,google/googletest,jlanecox/googletest,empiredan/googletest,xnagireddy/googletest