title: undefined method each_with_index activerecord-import
body: <p>I have a model in Rails for stock price history and I'd like to mass import that data from yahoo finance api into my model. </p>
  
  <p>This is what I have:</p>
  
  <pre><code>columns = [:date,:open,:high,:low,:close,:volume,:adjusted_close,:asset_symbol]
  values = ['2013-03-22',1,2,3,4,5,6,'YHOO']
  
  AssetHistory.import columns,values
  </code></pre>
  
  <p>Which results in an error saying: <code>undefined method each_with_index for '2013-03-22':String from .../activerecord-import/import.rb</code></p>
  
  <p>Note that the date in my values array is actually of type date in my model. (Is that the issue?)</p>
  
  <p>I am using Activerecord-import 0.3.1 and Rails 3.2. I am also using Postgresql if that matters.</p>
  
  <p>My Asset History model with annotation:</p>
  
  <pre><code># Table name: asset_histories
  #
  #  id             :integer          not null, primary key
  #  date           :date
  #  open           :float
  #  high           :float
  #  low            :float
  #  close          :float
  #  volume         :integer
  #  adjusted_close :float
  #  asset_symbol   :string(255)
  #  asset_id       :integer
  #
  
  class AssetHistory &lt; ActiveRecord::Base
    attr_accessible :adjusted_close, :close, :date, :high, :low, :open, :volume, :asset_id, :asset_symbol
    has_and_belongs_to_many :assets
    validates_uniqueness_of :asset_symbol, scope: [:date]
  end
  </code></pre>
  
  <p>Any reason what this issue is?</p>