Update 'README.md'

changed wording.

README.md

@@ -16,7 +16,7 @@ It does this by providing two macros:
 - `sing_add_trait`, which acts as an attribute to a trait implementation and gathers the method signatures that are used by `sing_loop!`.
 - `sing_loop!`, which takes a trait object and serialization/deserialization functions as well as some optional parameters. It generates a loop parsing function calls coming from STDIN (or any other `BufRead` stream), evaluating them by calling the appropriate method on the object and returning them on STDOUT (or any other `Write` stream).
 
-## Example usage
+## Usage example
 
 ```rust
 use serde::{Serialize, Deserialize};