Resolve normalised vs original distribution names

[takluyver]

trafficstars

At present, the distribution name comes from the wheel filename, which can be normalised according to the new rule (PEP 503 normalisation, but with _ in place of -) or according to an older rule (any character except A-Za-z0-9. is converted to _).

If we want the original distribution name for anything, we should get that from wheel metadata. If we want the normalised name, we should normalise it ourselves for consistency.