feat(emacs/lean-server): delete cache file (.clean) after visit/load
feat(emacs/lean-server): delete cache file (.clean) after visit/load

fix #75

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