What happened with `nalgebra::linalg::eigen`?

[Currently](https://github.com/dimforge/nalgebra/blob/122897ff16d99b81f45f2a014dc10c922b2a7262/src/linalg/mod.rs#L33) it is commented out with following comment:

```rust
// TODO: Not complete enough for publishing.
// This handles only cases where each eigenvalue has multiplicity one.
// mod eigen;
```

There are some commented out test and a commented out benchmark module for it too.

Start with the commented eigen module reference in src/linalg/mod.rs and inspect the commented-out tests and benchmark mentioned in the issue. Determine the current status and completeness requirements for nalgebra::linalg::eigen; the issue does not define a concrete completion criterion.

Written by the indexing model from the issue text.