Fixed displaying 'unit' attribute for Rack capacities

NOTE: You **need** to re-run the the sample_data.py script.
Fixed tests to support 'unit' attribute for Rack capacity
Merge pull request #74 from mfojtik/capacity_unit

Fixed displaying 'unit' attribute for Rack capacities
Improved handling of Rack state

- Set to 'provisioning' when Heat stack is CREATE_IN_PROGRESS
  or UPDATE_IN_PROGRESS

- Set to 'active' when Heat stack is UPDATE_COMPLETE or CREATE_COMPLETE

- Set to 'error' when Heat stack is UPDATE_FAILED or CREATE_FAILED
Merge pull request #70 from mfojtik/rack_state

Improved handling of Rack state