Add module_style lint to style
changelog: Add new [`module_style`] style lint
This is a configurable (no mod file/mod file) lint that determines if `mod.rs` is used consistently or if `mod.rs` is never used (using the new mod layout).
Add tests for disallowed_mod in ui-cargo test section
Use correct algorithm to determine if mod.rs is missing
Move to two lints and remove config option
Switch lint names so they read "warn on ..."
Emit the same help info for self_named_mod_file warnings
Bail when both lints are Allow
Reword help message for both module_style lints
Fix the versions of packages in the multiple_crate_versions ui test by
checking in the Cargo.lock for the test package. `ansi_term 0.11`
depends on `winapi ^0.3.4`. This means means that the expected stderr for
this test would have to be updated whenever `winapi 0.3` is updated
otherwise.
