Add assertions for real numbers

Apparently, real numbers can't be checked for equality using the `=` operator:

```
- (4.0 = 4.0);
stdIn:21.2-21.11 Error: operator and operand don't agree [equality type required]
  operator domain: ''Z * ''Z
  operand:         real * real
  in expression:
    4.0 = 4.0
```

I needed to assert against real numbers in my tests, so I added this.