go: fix snappy packing
go: fix unpacking arrays/hashes/refs/arrayrefs/hashrefs
go: return with error as soon as we detect it
go: improve reference handling
go: use our struct tags to encode special values
go: don't allow Marshal to panic()

un/marshalSafely are now not needed -- chainsaw.
go: be stricter about which files we load and test
go: test 28 makes Test::More::is_deeply crash :(
go: treat input buffer as read-only -- don't overwrite old one when we decompress
go: fix unpacking of sereal snappy v1 documents