Simplify composite lifecycle state

We now forbid calling setState or forceUpdate if any component's render function is higher in the stack, not just the component you're trying to update. (We do this already now for React.renderComponent and React.unmountComponentAtNode.)

This also has the advantage that we can now remove CompositeLifeCycle.RECEIVING_STATE, making _compositeLifeCycleState easier to reason about (not to mention that RECEIVING_STATE was a confusing name) and making it possible to remove a try/finally from the render path which might help with perf.
Also list <form> in error message as possible culprit
Fix IE8 potentially throwing during restoreSelection
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
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
Release materials for 0.11
Bump version for 0.12.0-alpha

[skip ci]
Merge pull request #1835 from amm385/patch-1

Update videos.md
Update 2014-07-17-react-v0.11.md
Fix appearance of video thumbnail
Merge pull request #1860 from KyleAMathews/patch-3

Not a candidate anymore
fix typo

Closes #1859.
Update Todo MVC example

A small patch for the Todo MVC example to use React 0.11.0.
This then allows the `MainSection` to return `null` instead of
previous `<noscript/>`.
getModifierState is case sensitive
Merge pull request #1837 from garrensmith/update-todo-example

Update Todo MVC example
Don't initialize reconcile transaction on server

...when calling setState from within a componentWillMount. Fixes #1866.

Test Plan: jest