fix(library/tools/tactic): 'cases' argument precedence
feat(library/tactic): add 'assert' tactic, closes #349
refactor(library/logic/heq): minor change
test(tests/lean/run/vector): use nat.add
refactor(data/nat/decl): use new naming convention at data/nat/decl.lean
chore(library/data/nat/decl): remove leftover
feat(frontends/lean): add 'prelude' command, and init directory
refactor(library): add 'init' folder
fix(tests/lean): adjust tests to modifications to standard library
chore(library/logic/logic.md): adjust documentation
fix(library/tactic/inversion_tactic): uninitialized variable