Allow option to redirect to error listing

[aDotInTheVoid]

The error listing is great, and std.rs should provide a shorthand for it.

I'd be willing to implement it, but I'm not sure of 2 things:

• Will the rust rewrite be merged, so should I wait for that.

• What should the urls look like:

  • std.rs/E0002
  • e.std.rs/E0002
  • std.rs/e/E0002 are all options.