npm publish

Hello.

I've published leaflet-plugins to npm: https://npmjs.org/package/leaflet-plugins
Now package pulls code from my forked repo, because I could not publish it by linking to your repo as there was no package.json.
This pull request adds package.json and changes the repo to be git@github.com:shramov/leaflet-plugins.git

After this pull request is merged, i could add someone to package owners list, so you'll be able to publish it as well.

Npm is a great package manager and I believe many people will be happy to have these wonderful plugins in the registry.

- Thanks,

Andrey