Fixing WARN on npm install for this package

Changing repositories to repository.

This prevents the warning from npm when installing this package.

I did not increment the version from 0.1.4, leaving that to the owner of the package to change as needed.

```
npm WARN package.json caching@0.1.4 'repositories' (plural) Not supported.
npm WARN package.json Please pick one as the 'repository' field
```