[TextField] allow use react element in TextField hintText

[ericfong]

We would like to use

 <TextField
 hintText={<span><i className="material-icons">search</i>Search...</span>}
 type="search" />

to put a material-icon into the hintText

I found that is working now. But with warning

Warning: Failed propType: Invalid prop `hintText` of type `object` supplied to `TextField`, expected `string`. Check the render method of `SearchBox`.

Please allow pass in react element. Thx

[MinThaMie]

+1 Happy that it works, but would like it without warning!

[hai-cea]

Fixed with #1424

[MinThaMie]

What way should it be implemented? Cause if I do it as in the example the warning stays and if I do it without the brackets it gives an compiler error