Clarify purpose of custom-elements-es5-adapter.js
Clarify purpose of custom-elements-es5-adapter.js

There is some confusion as to the purpose of the ES5 adapter (e.g., https://github.com/webcomponents/webcomponentsjs/issues/749) This clarifies that the adapter is not an ES5 polyfill but rather that it should be used if a project has been compiled to ES5.
webcomponents/polyfills,webcomponents/polyfills,webcomponents/polyfills