Refactor

- use an helper
- use yum cookbook
- use URI to create url
- Fix problem with "name" resource != new_resource.name
- Add a default value for `type`

Based on #2
- `yum` cookbook only depend on itself... as `apt` does...
- I can understand about `repo_gpgcheck` but this seems to be generally used on `[global]` section. In my point of view (and with an experience of ~30 cookbooks maintenance), reducing complexity and code duplication in this cookbook is far (and really far) better than this temporary lack. I will do a PR on yum to implement this option.