feat(library/tactic/generalize): add 'generalizes' syntax sugar, closes #327
refactor(library/data/nat/div): remove unnecessary annotations
feat(frontends/lean/placeholder_elaborator): apply substitution before collecting local instances, closes #333
feat(frontends/lean): allow user to associate precedence to binders, closes #323
feat(frontends/lean): allow user to associate precedence to binders, closes #323