recipe[10gen_repo]: update for yum cookbook >= 3.0.0

The `yum` cookbook introduced some non-backwards compatible changes in version `3.0.0`, one of them being a change in the attributes for the `yum_repository` LWRP. Namely, `url` is now `baseurl`, `action` should be `:create` instead of `:add` and `gpgcheck false` needs to be specified explicitly.

This commit introduces a dependency on `yum >= 3.0.0` and fixes the `10gen_repo` recipe to work with the new version.