Apply trickier gulp upgrades
Update react-streamfield, removing extraneous dependency
Upgrade to latest version of stylelint
Add package-lock.json changes from local npm install
* Remove useless CSS declaration
* Remove commented out styles
* Merge duplicate declarations
* Remove even more commented out code
* Move footer mq to footer declaration
* Remove more useless code
* Stop vendor prefixing for IE below 11
* Remove useless vendor prefixing
* Merge identical declarations
* Fix 1px overflow in content wrapper
* Fix explorer scrolling when open on mobile
* Remove unused import
* Add Redux performance measurements to explorer menu
* Rewrite explorer reducer to avoid unnecessary operations
* Stop changing reducer state on every action regardless of type
* Remove redundant children.isFetching property in nodes reducer
* Remove redundant children.isLoaded property in nodes reducer
* Remove redundant children.isError property in nodes reducer
* Refactor nodes explorer reducer with sub-reducer
* Fix linting issue
* Remove unused class name
* Change default icon className from empty string to null
* Remove old TODO comment
* Hoist icons in ExplorerItem component for better performance
* Add comment
* Add tooling for performance measurement of React components
* Clean up explorer panel component definition
* Make performance measurements opt-in
* Improve alignment of page explorer menu on mobile
* Close explorer on touchend rather than touchstart
* Comment out performance measurement code
* Remove fade transition completely
