urth-import fails with POLYMER package ECONFLICT

[bytesemantics]

Difficult one to solve - poss related to issue #31
Error:
[I 14:24:37.246 NotebookApp] Installing 'PolymerElements/paper-slider'
bower ECONFLICT Unable to find suitable version for polymer
[E 14:24:42.109 NotebookApp] Failed installing 'PolymerElements/paper-slider' into '/Users/bytesemantics/anaconda/share/jupyter/nbextensions/declarativewidgets' with cmd:
['bower', 'install', 'PolymerElements/paper-slider', '--allow-root', '--config.interactive=false', '--production', '--quiet']
due to: Command '['bower', 'install', 'PolymerElements/paper-slider', '--allow-root', '--config.interactive=false', '--production', '--quiet']' returned non-zero exit status 1
[W 14:24:42.111 NotebookApp] 400 POST /urth_import (::1) 4865.90ms referer=http://localhost:8888/notebooks/0001__JUPYTER_INTERACTIVE_DASHBOARDS/Untitled.ipynb

Where can I find docs on bower usage by declarativewidgets - i.e. do I need to bower init ? do I use the shipped bower.json?