Update readme since we're on crates.io now

README.md

@@ -20,7 +20,7 @@ people. Casaubon does what it is intended to do and no more.
 (requires [Cargo](https://doc.rust-lang.org/cargo/getting-started/installation.html))
 
 ```
-$ cargo install --git https://sr.ht/~simulacrumparty/casaubon
+$ cargo install casaubon
 ```
 
 ## Run tests