Add basic .gitignore file
Add basic .gitignore file

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

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