[Docs] Document PureRenderMixin addon

Fixes #1816
Update videos.md

Adding video for my recent talk in London about using React in large scale applications
Update videos.md

reordering to spot #4
[Docs] Update addons.update

Fixes #1815.
Add the new `$apply` command, plus a few examples.

@petehunt
Merge pull request #1817 from chenglou/docs-PureRenderMixin

[Docs] Document PureRenderMixin addon
[Docs] Perf tools

Fixes #1814.
@petehunt @joshduck
The images look blurry (taken on retina then shrank down to 50%...)
When proxying statics functions, copy properties

Test Plan: jest
Add destructuring visitor to JSX harmony transform
Merge pull request #1842 from spicyj/jstransform-visitors

Add new jstransform visitors to JSX transform
Fix comma splice
Reorder reference pages

This order should make more sense; it moves important functions like React.renderComponent up and deprecated/discouraged ones like transferPropsTo and setProps down. No content changes.
Add "Edit on GitHub" link on docs pages

Ember's docs do this and I rather like the idea of encouraging people to make improvements.
Merge pull request #1840 from spicyj/statics-proptypes

When proxying statics functions, copy properties
Merge pull request #1821 from chenglou/docs-addons-perf

[Docs] Perf tools
Merge pull request #1818 from chenglou/docs-apply

[Docs] Update addons.update
Update authors/acknowledgements [skip ci]
Add React.Children.count docs
Remove stale deprecation note from unmounting docs
Upgrade commoner dependency

0.9.5 depended on Node 0.11+, so make sure we don't ever get that.
See https://github.com/reactjs/commoner/pull/65
Performance boost in some cases