Hot-reload resets component variables to the initial state.

Given class A1
```js
class A1 extends Component {
constructor(){
this.myVariable1 = 1;
this.myVariable2 = 1;
this.myVariable3 = 1;
}
componentWillMount(){
this.myVariable1 = 10;
}
render(){
this.myVariable2++
}
}
```
Is hot replaced by the class A2
```js
class A1 extends Component {
constructor(){
this.myVariable1 = 2;
this.myVariable2 = 2;
this.myVariable3 = 2;
}
....
}
```

## Expected
`myVariable1` and `myVariable2` to keep their values, as long they were changed during the life time (#no-time-travel).
`myVariable3` to get the new value.

## Actual
all variables got updated.

## Reason
During the inject react-stand-in creates 2 classes - the old and the new. If variable got changed - the new value will be injected into instances.
It actually was made to transfer arrow functions, but will transfer all the class methods, regardless of the changes made in instances.

## Solution
Inject a new value, only if an existing variable matches the old one.