Draw tables with Unicode box drawing characters

Tables now look like this:

```
┌───────────────┬──────────────────────┐
│x              │ (and (car x)(cadr x))│
╞═══════════════╪══════════════════════╡
│[true, true]   │                 true │
├───────────────┼──────────────────────┤
│[true, false]  │                false │
├───────────────┼──────────────────────┤
│[false, true]  │                false │
├───────────────┼──────────────────────┤
│[false, false] │                false │
└───────────────┴──────────────────────┘
```

Although it looks a lot nicer in a terminal because there aren’t any spaces between the lines.