fix decode function with array types

[pthomalla]

fix to #12

[ayrat555]

@pgebal thanks for the review!
@pthomalla I'll merge it when @pgebal 's comments are resolved

[ayrat555]

lgtm. I'll test it tomorrow and release a new version if everything is ok

[ayrat555]

it still crashes when decoding example from the issue #12

[pthomalla]

function_selector =
  ABI.FunctionSelector.parse_specification_item(%{
    "type" => "function",
    "name" => "baz",
    "inputs" => [
      %{"name" => "value1", "type" => "uint32[]"},
      %{"name" => "value1", "type" => "uint32[]"}
    ],
    "outputs" => []
  })

data = ABI.TypeEncoder.encode([[1, 2, 3, 4], [4, 5, 6]], function_selector)
ABI.TypeDecode.decode(data, function_selector)

it works but method_id in FunctionSelector shout be set

I could turn off a check of method_id if this is preferred