[fixed] management of aria-hidden attribute

[kloots]

Fixes #601.

Changes proposed:
Decouples the management of the aria-hidden attribute from the code managing the class representing the open state

Acceptance Checklist:

• [x ] All commits have been squashed to one.
• [x ] The commit message follows the guidelines in CONTRIBUTING.md.
• [ x] Documentation (README.md) and examples have been updated as needed.
• [ x] If this is a code change, a spec testing the functionality has been added.
• [ x] If the commit message has [changed] or [removed], there is an upgrade path above.

[coveralls]

Coverage increased (+0.5%) to 86.829% when pulling abdd065 on kloots:fix-aria-hidden into 93b2c05 on reactjs:master.

[diasbruno]

Thank you , @kloots. I'll merge this later and release a new version after review #588.

[kloots]

That'd be great @diasbruno; this problem with aria-hidden has been plaguing us at Slack, so the sooner we can get the fix out the better. :)

[kloots]

@diasbruno any update on when you're going to do the next release so we can pickup this change for Slack?

[diasbruno]

Ok, I'll make a new release today.

[diasbruno]

Released v3.1.12.

Also, since Slack team is contributing to react-modal, it would be great if someone on the team join in to help manage this project. Let me know if you or someone on your team would like to join.