This adds a new property, `pluginId` which you can pass to `modifyClass`
which prevent the class from being modified over and over again.
This also includes a fix for polls which was leaking state between tests
which this new functionality exposed.
Per the linked site (http://mths.be/details) and https://caniuse.com/#feat=details the <details> element is supported since Chrome 12/Safari 6/Firefox 49/Edge 79. IE 11 doesn't handle them, but we dropped the support for that browser.
* Remove long-deprecated method
* FIX: Memory Leaks when decorating posts
Previously we'd keep creating mixins dynamically when decorating the
same class.
This code changes the API to recommend an `id` parameter for each
decorator which will avoid leaks. All plugins should be updated to
include this parameter, although if they don't in the meantime it'll
just mean a warning in the console (and a continued leak.)
