Feat(interceptors): Added interceptors

Added interceptors because I like this project.
Completes #5 

Simple Usage (in `config`):
```javascript
$sailsProvider.interceptors.push(['$q', function ($q) {
    return{
        request: function (config) {
            // ... stuff
            return config || $q.when(config);
        },
        response: function (response) {
            // ... stuff
            return response || $q.when(response);
        },
        requestError: function (config) {
            // ... stuff
            return $q.reject(reason);
        },
        responseError: function (response) {
            // ... stuff
            return $q.reject(reason);
        }
    }
}]);
```
Have as many as you want, push more to the `$sailsProvider.interceptors` array.
Should support the same things as [$http interceptors](http://code.angularjs.org/1.2.15/docs/api/ng/service/$http#interceptors).

I only tested it for my use case :(  Sorry no actual test scripts.