v0.3.0

[tony-iqlusion]

• usage: Use bold rather than explicit color (usage: Use bold rather than explicit color (fixes #105) #126)
• Switch from heck to ident_case (Switch from heck to ident_case (closes #100) #124)
• component: Ensure registration will succeed before mutating (component: Ensure registration will succeed before mutating #122)
• component: Add #[component(dep = "...")] attribute (component: Add #[component(inject = ...)] attribute #121)
• derive: Custom derive support for Component (derive: Custom derive support for Component #119)
• component: Index Registry by TypeId (component: Index Registry by TypeId #118)
• component: Add get_downcast_ref/get_downcast_mut to Registry (component: Add get_downcast_ref/get_downcast_mut to Registry #117)
• component: Add get_mut methods to Registry (component: Add get_mut methods to registry #115)
• component: Use generational-arena for component storage (component: Use generational-arena for component storage #113)
• component: allow Registry::iter() without mutable reference(Bugfix: allow Registry::iter() without mutable reference #110)