Add accessibility roles to pagination nav

[frrrances]

This PR adds an aria navigation role and a pager aria label for the nav element to improve accessibility.

[yuki24]

Thank you for your pull request. None of the maintainers including myself are familiar with accessibility. Could you elaborate on that? Also, we no longer accept feature requests for slim or haml templates. Could you remove the changes in the slim/haml templates from the commit?

[frrrances]

Sure thing - adding an aria role attribute to the nav element makes is much easier for screenreaders to find and use the navigation and it's what the W3C suggests:

https://www.w3.org/WAI/GL/wiki/Using_HTML5_nav_element

Adding a label let's the user differentiate between the different navs on the page. Here's a little more about marking up navigation for good accessibility:

http://www.a11ymatters.com/pattern/pagination/

And I've removed the changes to the slim and haml templates.

[yuki24]

@frrrances Thank you for the links - they are really helpful! It seems like individual page links should also have an aria-label or aria-current attribute, although the article you provided shows a way to assign them using javascript, and kaminari may not necessarily have to have them in the templates. What do you think? Thanks!

[frrrances]

@yuki24 Glad they were helpful! It would be nice to have the label and current for the individual pages but not critical. If you're interested, I can see about adding some JS for that as a separate PR, but I like how lean kaminari is :)

[yuki24]

@frrrances I've just merged this request in. I think this is a great first step toward adding better accessibility support. I agree that adding javascript would make kaminari less lean, and I think we could just hard-code an aria-label or aria-current attribute in the tag. Thanks again for your contribution!

[frrrances]

thanks @yuki24 ! Keep up the awesome work!