Add space-age

[BNAndras]

Related to #172.

I removed the usual examples from the function documentation since I didn't want to bias a student towards rounding to two digits or not.

Also, the Before block is awkward, but I couldn't define the predicate outside of it. The other option I saw was an Execute block, but that'll make the definition be seen as another test that passes every time (no assert). That's not a great solution.

[BNAndras]

Thanks, I borrowed the idea from a different track (forget which), and I use it every time I port space-age. It works nicely in Pyret (https://github.com/exercism/pyret/blob/main/exercises/practice/space-age/space-age-test.arr) since you can give a predicate to the standard is testing operator.

[kotp]

Thanks, I borrowed the idea from a different track (forget which), and I use it every time I port space-age. It works nicely in Pyret (https://github.com/exercism/pyret/blob/main/exercises/practice/space-age/space-age-test.arr) since you can give a predicate to the standard is testing operator.

Testing delta is useful for sure. "At least precise enough" is a good bar.