See the change for "changed" in json4s

Current output of json4s' `matchJson` in case of changes shows just one side of the diff (i.e. expected), e.g.
```
    "Changed:
    {"sources": "two"}"
```
It would be useful if it shown both sides. I.e. both expected and actual. Something like:
```
    "Changed, actual:
    {"sources": "one"}

   expected:
    {"sources": "two"}"
    "
```
