Change contentHiddenWhenClosed to set the css visibility instead of the html hidden property

[arye-eidelman]

This stops it from interfering with the content's scrollHeight fixing #194.

I've also added two tests for this prop.

[arye-eidelman]

If there were an is-transitioning or in-transition html class then content could be hidden via css selectors alone without needing to be an option in react-collapsible. Something like

.Collapsible.is-closed:not(.is-transitioning) ~ .Collapsible__contentOuter {
  visibility: hidden;
}

[codeability-ab]

Great that the bug is fixed! When can we expect it to be merged and released?

[karltaylor]

Great that the bug is fixed! When can we expect it to be merged and released?

Just want to make sure we're not going to regress, see my comment here https://github.com/glennflanagan/react-collapsible/issues/194#issuecomment-872289978

d4c8d7c was a fix for #177.

Does PR #195 fix both scenarios?