Rename raven to raven-js to better support browserify

[substack/browserify](https://github.com/substack/node-browserify) is an extremely popular client-side dependency solution. It uses npm as the package manager. Since I work in node, there is a conflict in npm with raven-node since both package.json files have the name listed as raven. It would be fantastic if you would consider changing the name.

Cheers :beers:!