Attributes hashes should respect symbolize keys

[soulcutter]

e.g.

xml = <<-XML
<params>
  <param name="Color">blue</param>
  <param name="Collection">Winter 2014/2015</param>
</params>
XML
parser = Saxerator.parser(xml) do |config|
  config.output_type = :hash
  config.symbolize_keys!
end

parser.for_tag(:param).each do |param|
  param.attributes # => { "name" => "Color" } SHOULD BE { :name => "Color" }
end

[soulcutter]

Fixed by #23