add readme to Cargo.toml, clippy is now content :)

Author: gpluscb

Cargo.toml

@@ -7,6 +7,7 @@ license = "MIT"
 repository = "https://github.com/gpluscb/cache-compute/"
 keywords = ["cache", "caching", "coalescing", "coalesce"]
 categories = ["asynchronous", "caching", "web-programming"]
+readme = "README.md"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html