fix(Makefile): not use latexmk due to old version problem in Ubuntu-12
fix(Makefile): not use latexmk due to old version problem in Ubuntu-12

cjmazey/fork_leanprover_tutorial,soonhokong/lean-tutorial,avigad/tutorial,soonhokong/lean-tutorial,leanprover/tutorial,Hodapp87/cs6460_project,fpvandoorn/tutorial,soonhokong/lean-tutorial,avigad/tutorial,avigad/tutorial,leanprover/tutorial,cjmazey/fork_leanprover_tutorial,fpvandoorn/tutorial,fpvandoorn/tutorial,Hodapp87/cs6460_project,leanprover/tutorial,cjmazey/fork_leanprover_tutorial,Hodapp87/cs6460_project