Release 0.4.0

Contains the following new features:
- node-set-provision-state accepts a --config-drive option
  which may be a file or a string, when setting the state to "active"
- node-show includes the new read-only driver_internal_info attribute

Contains the following fixes:
- node-set-maintenance-mode accepts true/false, instead of on/off,
  which was inconsistent with the REST API and python library
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