spec updates on power API

Hi all,

I pushed a few updates on the spec regarding the power API, part of what we discussed in the November thread. So basically the power API is not in the spec anymore, and implicitly handled by the polling API.
http://w3c.github.io/nfc/proposals/common/nfc.html

I also kept an eye on the Promises API evolution, since we are not making heavy assumptions on how they work besides the "then" method, which hasn't changed, I don't think we should be impacted.
https://github.com/domenic/promises-unwrapping

B.R.

Luc