Add a package.json file to allow npm installs.

I'm in the process of migrating from bower to npm for installing my frontend libraries, but I ran into an issue with SoundManager. Since it does not include a package.json file, I cannot install it even using a github url.

This PR adds a package.json file with author credentials. I versioned it at a pseudo-semver equivalent of the most recent release version. It's up to you if you want to publish it on npm, but having the file present in the repo would save a lot of people an extra build step.

I know you say in the readme to submit to the latest dev branch, but it didn't look like you were creating new dev branches any more.

Thanks.