Add `repository` field to `package.json`

Prevent `npm` from showing the `No repository field` warning.

![](https://cloud.githubusercontent.com/assets/1223565/2908714/d6b8b26e-d62a-11e3-9dc7-1e8a814860c5.png)


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@necolas I didn't wanted to basically "spam" you with this types of pull requests, but I think you should add the `repository` field in the `package.json` file of all components. Even if the warnings are harmless, having multiple components, will just make the them [pile up](https://cloud.githubusercontent.com/assets/1223565/2908862/7463f14e-d62c-11e3-8020-cad580ec92df.png), either annoying or confusing the user.