deps: upgrade npm to 2.7.1

[othiym23]

npm@2.7.1 is a pretty hefty release. I've included the four most significant changes below, and there are many others in the full CHANGELOG.md.

• 6823807
  #7121 npm install --save for Git
  dependencies saves the URL passed in, instead of the temporary directory used
  to clone the remote repo. Fixes using Git dependencies when shrinkwwapping.
  In the process, rewrote the Git dependency caching code. Again. No more
  single-letter variable names, and a much clearer workflow.
  (@othiym23)
• abdd040
read-package-json@1.3.2: Provide more helpful error messages when JSON
  parse errors are encountered by using a more forgiving JSON parser than
  JSON.parse. (@smikes)
• c56cfcd
  #7525 npm dedupe handles scoped
  packages. (@KidkArolis)
• 4ef1412
  #7075 If you try to tag a release
  as a valid semver range, npm publish and npm tag will error early instead
  of proceeding. (@smikes)

[misterdjules]

@othiym23 Moving to the 0.12.2 milestone because the current plan is to have v0.12.1 be v0.12.0 + the OpenSSL upgrade. Node v0.12.1 would thus ship with npm 2.5.1. I know it's different than our initial idea and what we talked about in #libuv. Do you have any objections to that?

[othiym23]

If it gets a patched 0.12.1 out faster, I have no objections, although I think the risk of including the upgraded npm is very low.

[misterdjules]

Thank you for your input @othiym23!

[misterdjules]

Closing in favor of #9443.