feat(emacs/lean-company): replace ?M in AC candidate with M and colorize

close #149
fix(emacs/lean-company): only activate auto-completion when TAB is pressed
fix(emacs/lean-tags): pass lean-flycheck-checker-options properly

Fix #153
feat(emacs/lean-settings): add lean-show-only-type-in-parens

Fix #135
feat(emacs/lean-cmd): add FINDG cmd
chore(frontends/lean/server.cpp): add BEGIN/END for WAIT command
feat(emacs/lean-cmd): add WAIT command
feat(emacs/lean-company): call FINDG if cursor is at "_"
feat(emacs/lean-settings): add lean-flycheck-pp-width and lean-flycheck-max-messages-to-display
feat(bin/linja): add --flycheck-max-messages

Close #134
checkpoint for imenu
flycheck checkpoint