Add script "guards" to docs examples

This was originally bundled in #102 but the windows CI there has blocked
that from landing quickly. These examples need to be fixed stat since
I've had at least a couple people notice it now when first trying out
the project.

README.rst

@@ -146,6 +146,7 @@ the hip new film we're shooting:
             print("CUTTTT CUUTT CUT!!! Donny!! You're supposed to say...")
 
 
+    if __name__ == '__main__':
         tractor.run(main)
 
 
@@ -192,6 +193,8 @@ and use the ``run_in_actor()`` method:
 
         print(await portal.result())
 
+
+    if __name__ == '__main__':
         tractor.run(main)