Refactoring

So, took some time but I've done some refactoring on the code. Most important, some API changes.

```progressbarProvider``` is now ```ngProgressProvider```
```progressbar``` is now ```ngProgress```

I've also added tests for the provider. Tests for the directive will come as well in a future.

Grunt have been added for running tasks like linting, concatenating, minifying and running tests. 

The provider have been splitted into 3 different modules. First is the provider which holds the whole progress logic. Then we have the directive which is the DOM and css that shows the progressbar. Then there is a module which just depends on the provider and directive for easy inclusion into your application.

Please have a look at this pull request and let me know of any errors, typos or generally bad practices. 

Thank all for the help with pull requests and issues! I deeply appreciate it!