Allow returning value when requiring/importing the lib

[Nargonath]

Would be nice if we could use the lib as is:

import angAccordion from 'ang-accordion';

angular.module('myApp', [angAccordion]);

instead of the current:

import 'ang-accordion';

angular.module('myApp', ['angAccordion']);

If you are ok with this, I'll be happy to make a PR. :+1:

Thanks for your library.

[uxxman]

Yes, sure. Thank you for the suggestion :)