Introduce configurable regex to use in ignoring requests

My use case was that I wanted to ignore all requests that matched a certain pattern. We have a couple of autocomplete endpoints that all end like '.../complete' which shouldn't show the loading bar. Providing configurable regex would allow you to easily and broadly apply request ignoring:

```javascript
.config(['cfpLoadingBarProvider', function(cfpLoadingBarProvider) {
    cfpLoadingBarProvider.urlsToIgnore = /.*\/complete/;
  }])
```