title: Tensorflow distribution object returning probabilties greater than 1
body: <p>Is there ever any reason a tendsorflow distribution object could return values greater than 1 for probabilities? </p>
  
  <p>This is the basic structure of my code.</p>
  
  <p>NN(input) is a neural network
  mu, sigma = NN(inputs)
  d = distributions.Normal(mu, sigma)</p>
  
  <p>(Get the probabilities of the targets.)
  probs = d.prob(targets)</p>
  
  <p>where mu, sigma and targets are shape [batch_size, 1]</p>
  
  <p>the probs start around 0.5 and as the model trains they gradually increase until they end up as high as 8! </p>