chore(library/coercion): cleanup
feat(frontends/lean): allow multiple coercions from class A to B, closes #187

See new tests (for examples)
tests/lean/run/coe10.lean
tests/lean/run/coe11.lean
tests/lean/run/coe9.lean

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(library/error_handling): generate valid line and column information
when in flycheck mode
fix(frontends/lean/parser): error line numbers for lua code, fixes #194
fix(lean-flycheck): make column optional when detecting error/messages

fix #194
fix(emacs/Makefile): add missing Makefile
fix(emacs/CMakeLists.txt): add all *.el files when install
feat(emacs/lean-company): add custom-variable lean-company-type-foreground

Close #190
fix(emacs/lean-company): import auto complete bug

fix #189
fix(emacs/lean-company): fix auto-complete behavior after tab

fix #192
fix(emacs/lean-mode): run company-lean--check-prefix before auto-complete

fix #191
fix(emacs/lean-mmm-lua): add 'insert' for mmm-insert-region (C-c % l)

Related issue: #74, https://github.com/flycheck/flycheck/issues/349, https://github.com/purcell/mmm-mode/issues/32