react 15.3.1

Improve performance of development builds in various ways. (@gaearon in #7461, #7463, #7483, #7488, #7491, #7510)
Cleanup internal hooks to improve performance of development builds. (@gaearon in #7464, #7472, #7481, #7496)
Upgrade fbjs to pick up another performance improvement from @gaearon for development builds. (@zpao in #7532)
Improve startup time of React in Node. (@zertosh in #7493)
Improve error message of React.Children.only. (@spicyj in #7514)

Avoid <input> validation warning from browsers when changing type. (@nhunzaker in #7333)
Avoid "Member not found" exception in IE10 when calling stopPropagation() in Synthetic Events. (@nhunzaker in #7343)
Fix issue resulting in inability to update some <input> elements in mobile browsers. (@keyanzhang in #7397)
Fix memory leak in server rendering. (@keyanzhang in #7410)
Fix issue resulting in <input type="range"> values not updating when changing min or max. (@troydemonbreun in #7486)
Add new warning for rare case of attempting to unmount a container owned by a different copy of React. (@ventuno in #7456)

Fix ReactTestInstance::toJSON() with empty top-level components. (@Morhaus in #7523)

Change trackedTouchCount invariant into a console.error for better reliability. (@yungsters in #7400)