Review application can mislead if a component is polyfilled

[NickColley]

Our review application uses the 'all' JavaScript bundle.

If a polyfill is defined in one component it can also solve issues in another component, without explicitly importing them.

We could consider only initialising components on their respective pages.

Work around: Uncomment other components when testing them.

This ties into #660

[kr8n3r]

Had a hard time trying to figure out why our classList polyfill wasn't working in IE8 tabs in the Design System.

Compared it to FT's script dependencies and found that it also needed the Element polyfill, which isn't imported in the our classList javascript file.

[36degrees]

Closing as once we've done #2506 we'll no longer be manually including polyfills in our JavaScript code.