deps: upgrade npm to 2.13.0

Now includes more npm ping, and also all the https://github.com/npm/npm/releases/tag/v2.13.0.

r: @Fishrock123 r: @chrisdickinson

(note for @Fishrock123: are there any additional patches we should be cherry-picking? I thought I saw some additional node-gyp changes in a PR a week or so ago, but I noticed that npm@2.12.1 only had the same two cherry-picked patches.)