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_November 23rd, 2018_
* Performance improvements by using PyYAML's CParser.
* Performance improvements by caching `get_link_variables()`
* when creating each container instance's environment variables
(by tedoc2000).
* Ability to define extra `/etc/hosts` entry by ship reference (requires
the ship to be defined using a numeric IP address).
* Added check for duplicate service instances names across services.
* Fix for the output column width calculations (by hgolson77).