Document Eclipse Integration

Using AutoValue in Eclipse results in Errors in the Workspace as eclipsec does not generate the Auto-Classes when running the incremental build. Perhaps you can provide some best-practices how to circumvent this problem.

There are some Tips out in the wild, like http://www.codeaffine.com/2014/03/04/using-the-autovalue-code-generator-in-eclipse/, but I think for most users the error will be enough of a showstopper to think the library (and not eclipse) is buggy.