Add equal value spec for unrelated objects

[mbj]

We fixed a similar issue on equalizer already. IHMO we should use equalizer also on veritas and this spec is to highlight the problem.

https://github.com/dkubb/equalizer/pull/7

I do not expect this is gets merged, only opening to start the discussion.

header = Veritas::Relation::Header.coerce([[:foo, String]])
relation = Veritas::Relation.new(header, [])
relation == Object.new # blows up and IMHO should return false

[dkubb]

This is resolved in https://github.com/dkubb/axiom/commit/89a5207785f3acf5d95748724b0742ae53a8dc00

[mbj]

@dkubb nice! thx.