Merge pull request #103 from pyviz/philippjfr/hv_import_fix

Update thumbnailer.py holoviews import

nbsite/thumbnailer.py

@@ -5,7 +5,7 @@
 from holoviews.ipython.preprocessors import OptsMagicProcessor, OutputMagicProcessor
 from holoviews.ipython.preprocessors import StripMagicsProcessor, wrap_cell_expression
 from holoviews.util.command import export_to_python
-from holoviews import Store, Dimensioned
+from holoviews.core import Store, Dimensioned
 
 import matplotlib.pyplot as plt
 plt.switch_backend('agg')