1. Removed duplication of code in stage component to avoid future
     potential divergence. Now just selectively applying styling based
     on states of zoomed, colorPicking, and question.

  2. Fixed bottom border getting chopped in zoomed mode by adding margin
     and adjusting height/width accordingly.

  3. Removed shouldComponentUpdate from stageHeader as suggested from code
     review. Added ignore lint warning suggesting change to stateless function.

This is for https://github.com/LLK/scratch-paint/pull/194, making the selector area smaller on tablet so as to create more space for the paint editor

Prevent switching tabs while one of these blocks is glowing from
crashing because it is given a new ID.

eslint-plugin-import doesn't like these inline loaders.

I tried unsuccessfully to configure the recommended solution with `eslint-import-resolver-webpack`, but we should come back to this.

With this change we only use `xhr` in the `CostumeCanvas` component.