feat(builder): Partial MethodBuilder impl

Including documentation at least on the method builder part. The
great thing is that fully working examples are now included on
every type !

Now more involved part starts ... namely setting up the individual call
method signatures.

src/rust/dev/mod.rs

@@ -43,7 +43,7 @@ impl<'a, C, NC, A> YouTube<C, NC, A>
     }
 
     pub fn videos(&'a self) -> videos::Service<'a, C, NC, A> {
-        videos::Service::new(&self.client, &self.auth)
+        videos::Service::new(&self)
     }
 }