Prepare for concurrent mode

[aleclarson]

In concurrent mode, renders can be discarded, which means they'll never be committed to the DOM (or whatever native host). There are potentially other issues as well (see here).

Currently, the withAuto and useAuto functions cause side effects during render, which means memory leaks will occur in concurrent mode.

[aleclarson]

The withAuto and useAuto functions no longer leak (since v0.3.0), but there are still issues in concurrent mode (if this is anything to go by). I'm going to wait until concurrent mode is released before doing anymore work on this.