Should parsing + pretty printing round trip?

ie this removes the `0`.

```
λ> DV.prettySemVer <$> DV.semver "2.2.1-b05"
Right "2.2.1-b5"
```

My use case is I was to convert a bunch of textual versions to `Version`, find the maximum, then get back the same textual representation for further use.

Not sure if this is a bug as such or a design decision.