ReactTransitionGroup: Fix changing to null child

Fixes #1457.

Test Plan: grunt fasttest
Merge pull request #1458 from spicyj/gh-1457

ReactTransitionGroup: Fix changing to null child
Move tooling info to Complementary Tools wiki

I moved the info that was here to the wiki page: https://github.com/facebook/react/wiki/Complementary-Tools; it doesn't need to live in the website any more.
Fix some linty things
Add basic CommonJS example with browserify
Merge pull request #1463 from andreypopp/example-commonjs

Add basic CommonJS example with browserify
Merge pull request #1459 from spicyj/ti

Move tooling info to Complementary Tools wiki
Merge pull request #1462 from spicyj/lint

Fix some linty things