Field.move keeps reference to old position

### Bug
when moving a field in a array from position 0 to lets say position 2 and then type in the input on position 2, the value of the input in position 0 will be updated instead of active input on position 2.

### What is the expected behavior?
To update the value of the current active input

### Sandbox Link
[https://codesandbox.io/s/oo367849lq](https://codesandbox.io/s/oo367849lq)

### What's your environment?
````json
"dependencies": {
"styled-components": "2.2.4",
"react-final-form-arrays": "2.0.1",
"react-final-form": "4.0.1",
"react-dom": "16.6.3",
"react": "16.6.3",
"final-form-arrays": "1.1.0",
"final-form": "4.11.0"
}
````