Fix touch actions on the stage

Lock scratch-* dependencies to their current versions

Update chromedriver to the latest version 

Update file-loader to the latest version 

Fix backdrop library 

Show newly added assets after they are loaded

Add musical instruments and letters to libraries

Localizes the pen extension:
- loads all pen locale information - may want to consider dynamically loading locales later.

Update xhr to the latest version 

Renamed meow sound to Meow

chore(package): update copy-webpack-plugin to version 4.3.0

Add full screen render view

  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.

Update react-modal to the latest version 

Add 'empty' sprite and costume

Check for the selected sound before rendering the editor

Make it so that the user cannot select tabs

Make libraries screen reader accessible.

chore(package): update webpack-dev-server to version 2.9.7

Enable sprite rotation keyboard control and standardize tabbing.