Update .gitignore
Update .gitignore

Signed-off-by: Leonardo de Moura <7610bae85f2b530654cc716772f1fe653373e892@microsoft.com>

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