title: Updating h5py Datasets
body: <p>Does any one have an idea for updating hdf5 datasets from h5py?
  Assuming we create a dataset like:</p>
  
  <pre><code>import h5py
  import numpy
  f = h5py.File('myfile.hdf5')
  dset = f.create_dataset('mydataset', data=numpy.ones((2,2),"=i4"))
  new_dset_value=numpy.zeros((3,3),"=i4")
  </code></pre>
  
  <p>Is it possible to extend the dset to a 3x3 numpy array?</p>