Add check for unused fields

[GoogleCodeExporter]

It would be awesome if EqualsVerifier could check for non-transient fields that 
are not used in the definition of "equals".  Frequently I use Eclipse to 
autogenerate equals/hashCode, but I might forget to re-generate after adding a 
new field.  

A suggested implementation and unit tests:

https://gist.github.com/1640709

https://gist.github.com/1640722

Original issue reported on code.google.com by pag...@gmail.com on 19 Jan 2012 at 10:50