lazy_static 1.4.0

on Rust Cargo

Bumps the minimum supported version of rustc to 1.27.2

• Fix typo in lib.rs (thanks @fbruetting)
• Automatically check if README.md examples are working when running "cargo test" (thanks @GuillaumeGomez)
• Allow deprecated to remove warnings in nightly (thanks @Schaeff)
• bump MSRV to 1.27.2 (thanks @matklad)