Update to Presentation API implementation status

I have updated the Implementation Status Wiki page [1] to reflect the
current implementation status of the Presentation API in Chrome/Chromium.

A recent change is to the format of supported URLs.  Following a request
from Mozilla [2], in Chrome 63 we have moved Cast and DIAL specific URLs to
their own URL schemes and out of the https://google.com namespace.

If you have sample applications that hard code these URLs, you will need to
migrate them to the new URL format.  I believe we are going to patch the
Web Platform Tests.

Details can be found in the Wiki document.

m.

[1]
https://www.w3.org/wiki/Second_Screen/Implementation_Status#Presentation_API
[2] https://www.w3.org/2016/05/25-webscreens-minutes.html#item03