[ttml2] WD for Wide Review Published

Per the decision from today's minutes, I have published a new WD of TTML2
for wide review at

https://www.w3.org/TR/2017/WD-ttml2-20170630/

If you run across any obvious typos or other forms of editorial breakage,
please let me know ASAP so I can update in place.

Regards,
Glenn