added package.json file for use with npm

Hi,

I created a package.json file for your lib to make it useable with npm in other projects thanks for your work :)

Feelic

Adding this file to the project would be very convenient! I will use a forked version of this repo until there is a package.json added. By merging this pull request you will also be able to close https://github.com/josephg/noisejs/issues/9 however i don't think anyone is bothered about adding a bower.json anymore.