another update to the Explainer

As discussed at the August 17 task force meeting I made a few small updates to the draft explainer document.

1) I changed the 1.2 heading from Use Cases to Use Case Examples.
2) I also added a sentence at the end of the opening paragraph for the Use cases: 

Personalization enables developers to create targeted extensions as additional use cases are encountered.

3) I updated the last paragraph of the 1.2.4 Severe Language Impairment section. I removed the previous paragraph about mis-translation and added the following.  It is a slight rewrite of what we discussed at the meeting:

Note that users learn a specific symbol vocabulary. However, the various vocabularies are mutually unintelligible. Personalization offers a mechanism to translate between symbol sets to allow people to communicate with one another where it was previously not possible.

You can review the draft at: https://raw.githack.com/w3c/personalization-semantics/explainer-compare/explainer.html <https://raw.githack.com/w3c/personalization-semantics/explainer-compare/explainer.html>

Becky Gibson
Sr. Accessibility Strategist
Knowbility.org

The World Wide Web Consortium (W3C), Web Accessibility Initiative (WAI)
Co-Chair, Accessible Platform Architectures	http://www.w3.org/wai/apa