Support for Node v4

[stephenplusplus]

master works already with 4, but not 0.20. We need to release a new version.

We should also update our travis.yml to include v4.

[jgeewax]

+1 to this -- let's try to get this out sometime this week?

[cdesiles]

I confirm this, cannot build gcloud npm dependencies with node v4

(quick workarround in your package.json deps: "gcloud": "git://github.com/GoogleCloudPlatform/gcloud-node#master")

[stephenplusplus]

@jokesterfr shortcut:

npm install --save googlecloudplatform/gcloud-node

But, v0.21.0 should release today after #856 merges.

[stephenplusplus]

Released and supported!

[cdesiles]

@stephenplusplus thanks a lot for the release!

[stephenplusplus]

Thanks for testing for us! Keep in touch :)