isEqual returns true by default


@erikras
This function is used to determine whether the fields are pristine or not, so if we have initial values and current form values - `[] and [{...},{...}]`, it shows that the values are pristine.
Could you please clarify the reason why it returns `true` in case of no callback is provided? I think it would be better to write it in the docs because it's quite confusing, I have expected it working this way - 'return this.props.a === this.props.b' by default instead of returning true when the custom callback is not provided, thanks!.
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