chore(frontends/lean/elaborator): minor cleanup
refactor(frontends/lean/elaborator): move local_context to separate file
chore(tests): use option -t 100000 to speedup tests
refactor(frontends/lean/elaborator): rename choice_elaborator to choice_iterator and move to separate module
feat(emacs/lean-server): handle modified buffer when send VISIT cmd

Close #159
fix(emacs/lean-server): respect order of messages in check-buffer-and-partition
fix(emacs/lean-tags): handle exceptions from find-tag
feat(emacs/lean-project): add lean-project-create to imenu

Related with #170