title: nodejs - Can't get paypal-ipn to work. Paypal keeps returning "INVALID"
body: <p>I'm trying to use the nodejs module paypal-ipn to verify a payment made to paypal.</p>
  
  <p>I pass into the verify method data in the following format...</p>
  
  <pre><code>{ tx: '60R52218GS3878125',
    st: 'Completed',
    amt: '0.01',
    cc: 'GBP',
    cm: '',
    item_number: '' }
  </code></pre>
  
  <p>Everytime I use it I keep getting "INVALID" as the response back from Paypal.</p>