Notification Settings: Add duration to notice after successfully saving

[ebinnion]

Addresses part of the issue in #3203.

This "should" cause the notices to disappear after a 4 second timeout. Although, in testing, I'm still noticing that a notice will stick around. I'm not sure why this is yet. And until we figure that out, it's pretty awkward that some notices will disappear while one or more won't.

@artpi suggested that this section be refactored such that the notices are included inline with each site's settings. cc @rickybanister for thoughts on that.

To test:

• Checkout update/me-notification-settings-notices branch
• Go to /me/notifications
• Update a setting for one of your site's and save.
• Update another setting and save. (quickly)

cc @rodrigoi who I believe wrote most of notification settings.

[rickybanister]

@ebinnion can you fill me in a bit more on the context here—are these global notices? How will the timeout be initiated? Can they just have dismiss links instead?

[rickybanister]

Ah, after looking at the initial issue, I think they should replace each other rather than time out.

cc @mtias

[BrookeDot]

After tested the patch, this still feels awkward showing multiple alerts on the page (even with some of them timing out. I would suggest going forward with one of the solutions that @rickybanister or @artpi suggested.

I would like to see inline alerts where we auto-save when checking/unchecking a box instead of having to click "Save Settings" button but that may be out of the scope of this alert.