put example: use uri parameter rahter than setting path components manually

Manipulating the path stays possible but is not something that should be
shown to newcomers first time they use the library, as it is much more
prone to errors.

Author: chrysn

clientPUT.py

@@ -30,11 +30,7 @@ async def main():
     await asyncio.sleep(2)
 
     payload = b"The quick brown fox jumps over the lazy dog.\n" * 30
-    request = Message(code=PUT, payload=payload)
-    # These direct assignments are an alternative to setting the URI like in
-    # the GET example:
-    request.opt.uri_host = '127.0.0.1'
-    request.opt.uri_path = ("other", "block")
+    request = Message(code=PUT, payload=payload, uri="coap://localhost/other/block")
 
     response = await context.request(request).response