Add test vector in ssz library

[GrapeBaBa]

@gballet any idea why this would happen? hashes_of_zero might not be sufficiently generated?

the gut feeling says this because Kai choose a genesis so far back that is slot 13436859 currently and this would have filled some slices in the state quite a lot (so basically around 13436859 items in a slice)

@GrapeBaBa can you add a test vector in ssz library for i) slice ii) array iii) List of such a size for lets say u8 type (bytes) and see ifs serialization/deserialization/merkelization passes

Originally posted by @g11tech in #178