feat(util/lean_path.cpp): add "exe_path/../lib/lean" to LEAN_PATH
feat(util/lean_path.cpp): add "exe_path/../lib/lean" to LEAN_PATH

Related issue: #223

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