Use new ref syntax

[jblanche]

According to https://facebook.github.io/react/docs/refs-and-the-dom.html

Using the ref callback just to set a property on the class is a common
pattern for accessing DOM elements.
If you are currently using this.refs.myRefName to access refs,
we recommend using this pattern instead.

[jblanche]

Bonus point, this fixes a weird error I was having.

Invariant Violation: addComponentAsRefTo(...): Only a ReactOwner can have refs.
You might be adding a ref to a component that was not created inside a component's `render`
method, or you have multiple copies of React loaded
(details: https://fb.me/react-refs-must-have-owner).

[coveralls]

Coverage increased (+0.4%) to 90.566% when pulling d19d702 on jblanche:newRefSyntax into a727336 on react-component:master.

[benjycui]

We had discussed this in antd.

It will be a breaking change.

[SomeoneWeird]

+1