Node: npm bump

Bumps npm back to the latest release. Hopefully [this issue](https://github.com/Homebrew/homebrew/issues/31777) will allow those still with issues to upgrade without issue. 

(For some reason, the Node Homebrew formula is still installing npm 2.0.0-alpha7 in its current format. This *seems* to fix that, but with Node/npm, who even knows how widely that'll be replicated for others).