Fix tooltips flicker

[mjackson]

Also, added another example with tooltips rendering inside a modal to try to replicate more closely the bug described by @bvaughn in #193.

Note: It was suggested in #193 that the bug was in the auto-id package since it provides null ids on the initial render. According to @ryanflorence this behavior is intentional. auto-id is not supposed to provide ids on the initial render because of the non-deterministic nature of server-rendered apps. Instead, they are supposed to be applied only after the initial render, to be used by screen readers.

Fixes #193
Closes #293

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[chaance]

Looks good to me 👍