Update package.json

Using this module as a dependency in a package.json file:

```
{
  "name": "test",
  "version": "0.0.1",
  "dependencies": {
    "text": "requirejs/text#2.0.10"
  }
}
```

Results in this warning:

```
npm WARN package.json text@2.0.10 'repositories' (plural) Not supported. Please pick one as the 'repository' field
```

This commit fixes that, according to the recommendation given by npm. :-)

Thanks for a great plugin!