User Story 21, (EXTENSION 1/4) User reviews are sortable

```
As a Visitor,
When I visit a user's show page to see their reviews,
I see additional links to sort their reviews in the following ways:
- sort reviews by highest rating, then by descending date
- sort reviews by lowest rating, then by ascending date
```

### Checklist:

- [ ] base code tests are written
- [ ] base code is written to pass tests
- [ ] edge case ("sad path") tests written
- [ ] edge case code written
- [ ] code is reviewed
- [ ] branch is merged
- [ ] all tests still pass

child of #5

child of #33

depends on #11