Fix odd formatting in ReactDOMComponent-test

Test Plan: Crossed fingers.
Test that text spans aren't remounted needlessly

While working on #2382, I accidentally broke this behavior (causing text components to get unmounted and remounted for any update) but we didn't have any unit test for it. Now we do.

Test Plan: jest TextComponent
Fix some minor typos in doc comments / code comments.
Merge pull request #2479 from spicyj/nitfix

Fix odd formatting in ReactDOMComponent-test
Merge pull request #2480 from spicyj/text-stability

Test that text spans aren't remounted needlessly
Merge pull request #2481 from mjul/fix-typos

Fix some minor typos in doc comments / code comments.
Add strokeOpacity to unitless CSS properties
Merge pull request #2482 from BinaryMuse/bkt/fix-stroke-opacity

Add strokeOpacity to unitless CSS properties
There's no isComponentOfType() anymore
Merge pull request #2498 from ikr/patch-1

There's no isComponentOfType() anymore
Merge branch 'master' of github.com:facebook/react