bump version to 0.9.0

Author: mainrs

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "env_logger"
 edition = "2018"
-version = "0.8.4"
+version = "0.9.0"
 authors = ["The Rust Project Developers"]
 license = "MIT/Apache-2.0"
 readme = "README.md"