add `ReactComponentWithPureRenderMixin` to addons
Remove leftovers from ReactTransitionGroup rewrite

Looks like while rewriting @petehunt forgot to remove this block.
See: 9ac27cb551b85293d03d334363acd7cf9c77813a
This block used to contain the only `runNextTick` ocurrences in the whole project.
No tests broken after removal, no documentation affected.
Update mailmap post 0.10 (see #1283)
Merge pull request #1329 from irae/transition-group-leftovers

Remove leftovers from ReactTransitionGroup rewrite
[docs] Amend "References to components" tip to mention descriptors.
Simplify comment.
Remove erroneous line about static methods.
Merge pull request #1345 from kmeht/referenceDoc

[docs] Amend "References to components" tip to mention descriptors.
Merge pull request #1308 from chenglou/pure

add `ReactComponentWithPureRenderMixin` to addons
Remove toJSON

This was temporarily needed since clone on mount introduced a cyclic reference
in __DEV__. This reverts that change since we now have descriptors.

To avoid a problem where toJSON may collide.