Keys shim misses non enumerable properties

Currently the `_.matches` tests fail in IE<9 because of this bug.

Tested in ie7 and ie8
This is probably the most common object iteration bug as it's addressed in many libs. You'd want to use a flag for this to avoid extra work when not-needed and to make fixing other `for-in` cases too. This is one reason why I [abstract it a bit more](https://github.com/lodash/lodash/blob/4b5c54e2401e8069cdde7743d8e37a9c2f2a58bf/dist/lodash.compat.js#L7431-L7483).