deps upgrade npm to 2.5.1

[othiym23]

From the release notes:

This release doesn't look like much, but considerable effort went into ensuring that npm's tests will pass on io.js 1.1.0 and Node 0.11.16 / 0.12.0 on both OS X and Linux.

NOTE: there are no actual changes to npm's code in npm@2.5.1. Only test code (and the upgrade of request to the latest version) has changed.

npm-registry-mock@1.0.0:

• 0e8d473 #7281 npm-registry-mock@1.0.0: Clean up API, set connection: close.
  (@robertkowalski)
• 4707bba
  Further update tests to work with npm-registry-mock@1.0.0.
  (@othiym23)
• 41a0f89
  Got rid of completely gratuitous global config manipulation in tests.
  (@othiym23)

MINOR DEPENDENCY TWEAK

• a4c7af9
request@2.53.0: Tweaks to tunneling proxy behavior.
  (@nylen)

Also includes a patch to node's Makefile that more tightly constrains the $PATH available to npm when running make test-npm.

[DomT4]

@othiym23 Does this remove the need to patch npm for iojs?

[othiym23]

@DomT4 this is unrelated to that issue, which requires that nodejs/node-gyp#564, or something like it, be merged and a new version of node-gyp be published.

[DomT4]

Ah I see, Thanks Forrest.

[tjfontaine]

@misterdjules had already been working to verify the tests this morning, thanks @othiym23 for submitting this PR

LGTM

[misterdjules]

The upgrade to npm 2.5.1 LGTM, thank you again @othiym23 for your help!

However I'd like to leave out the change to the Makefile for now because I'd rather take the time to review it carefully, which I can't do properly now.

I had submitted a similar PR that makes test-npm use the node binary built from the local checkout. One of the differences with your commit is that it preserves $PATH, I'm not sure if it's better, but let's discuss that over there if you don't mind.

[misterdjules]

Landed in 087a751, thank you!