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
Adding "appear" phase to ReactTransitionGroup and ReactCSSTransitionGroup.

"appear" differs from "enter" in that all children of a transition group at mount time will "appear" but will not "enter". All children later added to an existing transition group will "enter" but not "appear".

This extra transition phase allows for animation-on-mount effects.

A mirroring "appear" prop has been added to ReactCSSTransitionGroup, however for reverse-compatibility (and because "appear" is less common) it defaults to false.

Thanks to @afa for his work investigating the possible ways to implement this.
Update ref-09-glossary.md
Merge pull request #2512 from leebyron/transition-appear

Adding "appear" phase to ReactTransitionGroup and ReactCSSTransitionGroup
Merge pull request #2514 from jvalente/patch-1

Update ref-09-glossary.md