Revise dpub note

closes #546

@pkra - I've revised the note.  based on your latest github comment, it still seems a warning is in order.  using dpub for standard web dev is not the intent of dpub aria, after all.  if it was, then then the features would be in ARIA proper :)

please let me know if there are any further changes you'd like to see with this note or make any suggested edits you think would make it better.

thanks for calling this out and doing some testing.

Author: scottaohara

index.html

@@ -495,9 +495,10 @@ <h2 id="docconformance">
         is NOT RECOMMENDED, in some  situations explicitly setting these attributes can be helpful – for instance, 
         for user agents that do not expose implicit ARIA semantics for certain elements.
       </p>
-       <p class="note" id="dpub-usage-note">
-        While it is conforming to use [[[dpub-aria-1.0]]] `role` values as outlined in the following table, the current support for 
-        exposing the semantics of these values to users of assistive technology is close to non-existent.
+      <p class="note" id="dpub-usage-note">
+        While it is conforming to use [[[dpub-aria-1.0]]] `role` values as outlined in the following table, the use of these roles
+        is not intended for implementation of websites. If using these role for purposes beyond the scope of the digital publishing 
+        industry, further manual testing will be necessary to ensure the intended experience is provided to users.
       </p>
       <table class="data">
         <caption>