0.5.0

• Transition to Rust 2018. With this change, the minimum required version will go up to Rust 1.31.

• Reduced the feature of "std" crate feature. The current "std" crate feature only determines whether to enable std library's traits (e.g., std::io::Read) support. "std" crate feature is enabled by default, but you can reduce compile time by disabling this feature.

• Fixed problem where "macro attributes must be placed before #[derive]" error occurred when #[enum_derive] attribute was used with other attributes.

• No longer need #[macro_use] extern crate auto_enums;. You can use #[auto_enum] attribute by use auto_enums::auto_enum;.

• Removed "unstable" crate feature.