Cargo: bump to version 4.0.0

Cargo.toml

 [package]
 name = "seahash"
-version = "3.0.7"
-authors = ["ticki <ticki@users.noreply.github.com>"]
+version = "4.0.0"
+authors = ["ticki <ticki@users.noreply.github.com>", "Tom Almeida <tommoa256@gmail.com>"]
 description = "A blazingly fast, portable hash function with proven statistical guarantees."
 repository = "https://gitlab.redox-os.org/redox-os/seahash"
 documentation = "https://docs.rs/seahash"