Update .travis.yml
Update .travis.yml

 - clean up builds
 - remove flex/bison
 - have separate memcheck build, doxygen build, and testcov build

dselsam/lean,fgdorais/lean,javra/lean,c-cube/lean,avigad/lean,javra/lean,leanprover-community/lean,avigad/lean,digama0/lean,fpvandoorn/lean,Kha/lean,soonhokong/lean-windows,levnach/lean,levnach/lean,levnach/lean,c-cube/lean,soonhokong/travis_test,fgdorais/lean,eigengrau/lean,leanprover-community/lean,leanprover/lean,sp3ctum/lean,leodemoura/lean,fgdorais/lean,eigengrau/lean,UlrikBuchholtz/lean,javra/lean,leanprover/lean,Kha/lean,fpvandoorn/lean2,soonhokong/lean-osx,avigad/lean,leanprover-community/lean,digama0/lean,leodemoura/lean,soonhokong/lean-osx,avigad/lean,soonhokong/travis_test,soonhokong/travis_test,htzh/lean,dselsam/lean,soonhokong/lean,leodemoura/lean,leanprover/lean,dselsam/lean,soonhokong/lean-windows,avigad/lean,digama0/lean,digama0/lean,rlewis1988/lean,johoelzl/lean,leanprover/lean,johoelzl/lean,rlewis1988/lean,fgdorais/lean,soonhokong/lean-osx,leanprover/lean,johoelzl/lean,htzh/lean,fpvandoorn/lean2,dselsam/lean,sp3ctum/lean,UlrikBuchholtz/lean,c-cube/lean,htzh/lean,leodemoura/lean,sp3ctum/lean,fpvandoorn/lean,johoelzl/lean,leodemoura/lean,eigengrau/lean,Kha/lean,soonhokong/travis_test,rlewis1988/lean,fpvandoorn/lean2,fpvandoorn/lean,fpvandoorn/lean,fpvandoorn/lean2,levnach/lean,UlrikBuchholtz/lean,Kha/lean,soonhokong/lean-windows,soonhokong/lean-osx,dselsam/lean,soonhokong/lean,digama0/lean,codyroux/lean0.1,levnach/lean,leanprover-community/lean,sp3ctum/lean,codyroux/lean0.1,htzh/lean,dselsam/lean,UlrikBuchholtz/lean,soonhokong/lean,leodemoura/lean,leanprover-community/lean,digama0/lean,sp3ctum/lean,soonhokong/lean,leanprover-community/lean,htzh/lean,eigengrau/lean,fpvandoorn/lean,fpvandoorn/lean2,Kha/lean,codyroux/lean0.1,soonhokong/lean-osx,johoelzl/lean,javra/lean,rlewis1988/lean,fpvandoorn/lean,javra/lean,soonhokong/lean-windows,Kha/lean,rlewis1988/lean,codyroux/lean0.1,leanprover/lean,rlewis1988/lean,avigad/lean,UlrikBuchholtz/lean,soonhokong/lean-windows,johoelzl/lean,fgdorais/lean,soonhokong/lean,c-cube/lean,c-cube/lean,eigengrau/lean,fgdorais/lean