Handle className properly on SVG nodes

This strategy avoids a runtime check for every set (as opposed to using a mutation method).

Test Plan: Verify that changing className works on a div and a rect in latest Chrome, latest Firefox, IE9. Verify that the div works in IE8.
Merge pull request #1590 from spicyj/svg-classname

Handle className properly on SVG nodes
Fix tutorial to have exact translation of example

Fixes #903.
Sync upstream modules

crateObjectFrom is no longer used (was used in ReactPropTypes). Others are small changes.
Update findComponentRoot and processUpdates warnings for SVG

I ran into a really difficult-to-debug issue with a React app with SVG
elements. Christopher sat down with me for a while and we finally figured out
that the browser was moving non-SVG elements out of a parent `<svg>` node which
triggered the `processUpdates()` invariant. This updates the error message
thrown from there to include this scenario in the possible issues list.
[docs] Fix grammar
Reference Jest in TestUtils documentation.
Merge pull request #1620 from kmeht/jestDoc

Reference Jest in TestUtils documentation.
[Blog] One-year anniversary post
Merge pull request #1614 from chenglou/1-year

[Blog] One-year anniversary post
Typo: ClosureScript -> ClojureScript
Merge pull request #1627 from Enome/master

Typo: ClosureScript -> ClojureScript in latest blog post
Fix onLoad and onError on images

Fixes bug introduced in c62c2c5.

Test Plan: Tested that the onLoad event was properly triggered on an image. Didn't test onError but I can only assume that it works equally well.
Merge pull request #1632 from spicyj/img-load-error

Fix onLoad and onError on images
Fix getEventModifierState, no allocations

Alternative to #1637 that doesn't allocate on every event.

Test Plan: Crossed fingers.
Merge pull request #1638 from spicyj/getmodifierstate-2

Fix getEventModifierState, no allocations