Fix live editor examples on home page.

Remember that one time I wrote release notes and said:

> This is a breaking change - if you were using class, you must change
> this to className or your components will be visually broken.

Good thing I didn't listen to myself!
Add clickable anchors to docs headers

Closes #434
docs: remove OUTLINE
docs: Delete Mutation Events (onCharacterDOMModified)
ReactTransitionGroup example: fix typo and logic bug in handleRemove
Update API docs for unmountAndReleaseReactRootNode
Make SelectEventPlugin not throw for range inputs

Accessing .selectionStart on a non-text input will throw (see http://www.w3.org/TR/2009/WD-html5-20090423/editing.html#textFieldSelection), so check that the input has selection capabilities before accessing the property.

Fixes #437.
Don't reset mouseDown in focus handlers

Focus fires after mouse down on initial click, so we lost the
flag when the user initially began dragging on the input.
fixed %d in invariant call
Fix ReactTransitionEvents detectEvents
Fix unmounting components mounted into doc element

If we are to unmount a component mounted into a document element we should
unmount it from document.documentElement and not from document.firstChild which
is a doctype element in this specific case.
Make 'disabled' MUST_USE_ATTRIBUTE for compatibility with CSS [disabled] selectors.

When a ReactDOMComponent is created with the property `disabled: true` subsequently setting the property to `disabled: false` the HTML attribute `disabled="true"` was being left in the DOM.
npm shrinkwrap

We should be doing this in the stable branch to ensure fuzzy
dependencies are met identically on subsequent releases.

In this case, browserify had a change in 2.34.3 which resulted in
JSXTransformer to be a different size. While it was a change for the
better, it was unexpected and not a change we were calling out in the
release.

This shrinkwraps to the same versions of packages we had when we shipped
0.5.0.
Update everything for v0.5.1
blog post for 0.5.1
Move heading anchors 50px up to avoid nav bar

Fixes #447.

We do this by moving the actual anchored element up in the page without moving the actual text. (Apple uses a similar trick in their framed docs.) Now this looks a bit sillier on smaller screens but it's better overall.
Update tutorial to use className
[docs] Clarify when `getInitialState` is called.
"Thinking in React" blog post
tutorial: Simplify ajax options

dataType was unnecessary; mimeType was both unnecessary and wrong in this case. Also removed an unnecessary bind and changed pollInterval to 2000 ms for consistency with https://github.com/petehunt/react-tutorial (faster is nicer if you actually try it out!).