Changed some parameters on directive to make their values dynamic.

In my app I have 3 environments: `development`, `staging` and `production`. Is common to have something like this, and use environment variables or a configuration file per environment to manage some data, like services API's IDs, secrets keys, etc.

Because of that I changed some parameters to allow me to send a object/variable instead of a plain string.

For now I'm using my own repository, but would be nice to use the original again.

Please, let me know your thoughts about this PR.