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
Warn when casing CSS vendor prefixes incorrectly

Fixes #2487.

Test Plan: jest
Stop treating key={null} as an unspecified key

This reverts commit dd92786fb038c4eb7c6545928646ec8aa9ecfa36, which was intended to be temporary for the 0.12 release.

Fixes #2394.