added a functionality to configure directive from app.config and add spe...

Hey Dan

I came across a use case in which I wanted to show the loader in the app with the exception on some APIs. Currently the overlay did not support that so I did some tweaks to achieve the above:

1) Added a Provider through which I can configure "delay" and "urls" on which I dont want to show the loader on. It also contains the default config for the overlay.
2) Directive now looks at its scope for delay, if it doesn't find it, it picks up the delay from config
3) Before processing request to show the overlay, the directive first looks for the url in the exceptions provided in the config, if that url exists as an exception, the loader is not displayed and the API proceeds.

This might be helpful to you or someone else who has a similar use case.

Thanks :)