raise InvalidWheelFilename if version is missing in wheel filename

Wheel('Cython-cp27-none-linux_x86_64.whl') did raise an AttributeError
instead of InvalidWheelFilename.

This has also been discussed an is similar to
https://github.com/pypa/pip/pull/1445
fix typo in test name
Merge pull request #1476 from schmir/require-version-in-wheel-filename

Require version in wheel filename