Update README.md

README.md

@@ -44,10 +44,12 @@ fn parse_proto(data: &[u8]) -> Result<String> {
 
 ```rust
 let mut buf = [0u8; 1024];
-let mut builder = ProtoBuilder::new(&mut buf);
-builder.write_string(1, "hello world")?;
-builder.write_int32(2, 42)?;
-let data = builder.finish()?; // returns the used slice of the buffer
+let mut builder = HelloProto::Builder::new(&mut buf)
+    .hello_world("some world")
+    .inner_world() // Returns an HelloProto::InnerWorld::Builder 
+        .thought("some thought")
+        .done(); // returns the HelloProto::Builder
+let bytes_written = builder.finish()?; // returns the number of bytes written to buffer
 ```
 
 ### High level design