Issue title: Incorrect cursor when rendered inside a link due to inline styles
 Issue body: Hey, thanks for the great component. We're using it on all our product and product listing pages.

We noticed an issue caused by the RatingSymbol inline `cursor` style here: https://github.com/dreyescat/react-rating/blob/master/src/RatingSymbol.jsx#L43

If a `readonly` rating is rendered inside a link (in order to, say, take you to that item's reviews page), Chrome at least surprisingly doesn't render `cursor: auto` as a pointer – so there's no indication that you can click the link.

Using `cursor: inherit` instead makes it work, although I wonder if that would render an incorrect cursor in other situations?

For now we're working around this by applying some additional CSS to our `fullSymbol` and `emptySymbol` components, but it would be nice if it worked out of the box.


 Comments: 
 Comment 0: I like it!

I think inheriting parent computed value for the mouse pointer when the rating is read only is a better default than `auto`.

 Comment 1: Released in version [1.2.1](https://github.com/dreyescat/react-rating/releases/tag/v1.2.1).
{'source': 'GithubIssues', 'repo_name_with_owner': 'dreyescat/react-rating', 'issue_id': 333834950, 'repo_stars': 513.0}