v0.4.0

Added

• Debug, Eq, PartialEq, Serialize, and Deserialize traits are added to the registry module.
• schedule! macro for defining a schedule.
• Schedule! macro for defining the type of a schedule.
• schedule::task module for defining tasks that make up schedules.
• Clone implementation for World.

Changed

• Send and Sync implementations of World now only require the registry to implement Registry + Send and Registry + Sync respectively.
• Lifetime in System and ParSystem traits has been moved to the Views associated type.
• The generic lifetimes on the system::schedule::RawTask and system::Stages traits have been removed.
• Registry is now explicitly bound to the static lifetime. This was previously only implicit, with Registrys being made of Components which were bound to 'static.
• Both System and ParSystem no longer require a lifetime bound on the Registry R in their run() methods.
• Schedule has been changed from a struct to a trait.
• Schedules now have their stages defined at compile-time.
• registry! macro has been renamed to Registry! to indicate that it is intended to be a type-level macro.
• views! macro has been renamed to Views! to indicate that it is intended to be a type-level macro.

Removed

• system::Null is removed, since it is no longer needed for defining a Schedule.
• schedule::Builder is removed, since it is no longer needed for defining a Schedule.
• The schedule::raw_task module has been removed. There is now no distinction between a raw task and a regular task.
• The schedule::stage module has been removed. It still exists as part of the private API, but is no longer exposed publicly.
• The schedule::stages! macro is removed. Schedules are no longer defined in terms of their stages directly, but are defined in terms of their tasks using the schedule! and Schedule! macros.

Fixed

• Mitigated potential bug regarding the way non-root macros are exported when compiling documentation. Previously, a change in Rust's experimental macro syntax could have potentially broken usage of the library for all users. Now, a change in the syntax will only break building of the documentation (using --cfg doc_cfg), which is acceptable.
• World::shrink_to_fit() is no longer unsound. There were issues previously with it improperly deleting archetypes.