Bump version.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "smoltcp"
-version = "0.4.0-pre"
+version = "0.4.0"
 authors = ["whitequark <whitequark@whitequark.org>"]
 description = "A TCP/IP stack designed for bare-metal, real-time systems without a heap."
 documentation = "https://docs.rs/smoltcp/"

README.md

@@ -77,7 +77,7 @@ To use the _smoltcp_ library in your project, add the following to `Cargo.toml`:
 
 ```toml
 [dependencies]
-smoltcp = "0.3"
+smoltcp = "0.4"
 ```
 
 The default configuration assumes a hosted environment, for ease of evaluation.
@@ -85,7 +85,7 @@ You probably want to disable default features and configure them one by one:
 
 ```toml
 [dependencies]
-smoltcp = { version = "0.3", default-features = false, features = ["..."] }
+smoltcp = { version = "0.4", default-features = false, features = ["log"] }
 ```
 
 ### Feature `std`