Add npm/browserify support

This PR makes the plugin compatible with npm/browserify, and also theoretically with AMD/RequireJS. 

Without this change, it becomes a bit tedious to use the plugin in projects where the rest of the build/dependencies are managed by npm.

I've added a ```package.json``` with version number 0.1.0 - feel free to change it if you feel another number better represents the state of the plugin.