Unexpected Output

Sorry, it's me again.

```nim
nim> import struct
nim> var a = unpack(">3I", "Hello World ")
nim> a
@[1214606444, 1864390511, 1919706144] == type seq[StructNode]
nim> pack(">3I", a)
Horld  == type string
```

Also it would be a useful feature to pass a `seq[int32]` to `pack`.