fix multiple %01 wildcards

multiple off-by-ones, wrong syntax and stale constants on two lines

fixes #7 but I think there should be some tests as well

This works now:

```python
>>> CPE2_3_URI('cpe:/a:microsoft:internet_explorer:%01%018.%02:%02s%01%01%01').as_wfn()
'wfn:[part="a", vendor="microsoft", product="internet_explorer", version="??8\\.*", update="*s???"]'
```