Hide some components rather than unmounting them to allow to show again
quickly and keep the view state such as the scrolled offset.

- Deleting a toot
- Muting, blocking someone
- Clearing notifications

Remove source map generation from development environment, as it is a huge
performance sink hole with little gains

* Remove deprecated features at React v15.5

- [x] React.PropTypes
- [x] react-addons-pure-render-mixin
- [x] react-addons-test-utils

* Uncommented out & Add browserify_rails options

* re-add react-addons-shallow

* Fix syntax error from resolve conflicts

* follow up 59a77923b3

Also, since the root component connects to the stream that updates home/notification columns,
there is pretty much no case for refreshing those columns beyond initial load. So, move the
loading of those columns into the root component, to prevent unneccessary reloads when switching tabs
on mobile or resizing desktop window between mobile/desktop layouts

in the column and what appears as desktop notifications. Settings do not
persist yet