Update NPM to V5

[janpieterz]

The speed benefits are incredible, and there are quite some complaints about the NPM speed currently:
#553

More information: https://github.com/npm/npm/releases/tag/v5.0.0

[chrispat]

Currently NPM 5 is not shipped with the node LTS. As we move to the next Node LTS we will get the version of NPM that matches.

[bryanmacfarlane]

Is the request to update the hosted pool image? (note the agent uses the installed npm on the box so it's not an agent thing)

[janpieterz]

Yeah this'd be for the hosted pool image, but I understand the choice for LTS versions!

[chrispat]

@janpieterz as I mentioned in the previous comment we currently keep the pool on the most recent LTS. We do have a new task in the list called the Node Tool Installer that will let you install an arbitrary version of Node and optionally include the version of NPM that goes along with it. Putting that in place should let you use any version of Node and NPM that you need.