Use with calculation decorator

### Are you submitting a **bug report** or a **feature request**?
**bug report**

### What is the current behavior?
If remove array item other items will be changed

### What is the expected behavior?
Other items should not be changed
### Sandbox Link
https://codesandbox.io/s/7z85xxz8mx
try to remove the first row
### What's your environment?
"final-form": "4.7.3",
"final-form-arrays": "1.0.4",
"final-form-calculate": "1.2.0",
"react": "16.4.0",
"react-dom": "16.4.0",
"react-final-form": "3.5.1",
"react-final-form-arrays": "1.0.4",

Start with the linked CodeSandbox and reproduce the issue by removing the first row while using final-form 4.7.3, final-form-arrays 1.0.4, final-form-calculate 1.2.0, react-final-form 3.5.1, and react-final-form-arrays 1.0.4. Trace the calculation decorator and array behavior shown there; done means removing one item leaves all other items unchanged.

Written by the indexing model from the issue text.