travis: only test on master branch
travis: only test on master branch

cr-marcstevens/fplll,shi-bai/fplll,dstehle/fplll,fplll/fplll,blowfish880/fplll,fplll/fplll,fplll/fplll,blowfish880/fplll,blowfish880/fplll,shi-bai/fplll,shi-bai/fplll,shi-bai/fplll,cr-marcstevens/fplll,fplll/fplll,dstehle/fplll,fplll/fplll,cr-marcstevens/fplll,cr-marcstevens/fplll,dstehle/fplll