title: PyTorch Lightning - Display metrics after validation epoch
body: <p>I've implemented <code>validation_epoch_end</code> to produce and log metrics, and when I run <code>trainer.validate</code>, the metrics appear in my notebook.</p>
  <p>However, when I run <code>trainer.fit</code>, only the training metrics appear; not the validation ones.</p>
  <p>The validation step is still being run (because the validation code calls a <code>print</code> statement, which <em>does</em> appear), but the validation metrics don't appear, even though they're logged.  Or, if they do appear, the next epoch immediately erases them, so that I can't see them.</p>
  <p>(Likewise, tensorboard sees the validation metrics)</p>
  <p>How can I see the validation epoch end metrics in a notebook, as each epoch occurs?</p>