Add deregister and revisions command

[fujiwara]

Add deregister command to deregister task definitions.
Add revisions command to list / describe task definition revisions.

usage: ecspresso deregister [<flags>]

deregister task definition

Flags:
  --help                    Show context-sensitive help (also try --help-long and
                            --help-man).
  --config="ecspresso.yml"  config file
  --debug                   enable debug log
  --envfile=ENVFILE ...     environment files
  --color                   enable colored output
  --dry-run                 dry-run
  --revision=REVISION       revision
  --keeps=KEEPS             numbers of keep latest revisions except in-use
  --force                   deregister without confirmation

usage: ecspresso revisions [<flags>]

show revisions of task definitions

Flags:
  --help                    Show context-sensitive help (also try --help-long and
                            --help-man).
  --config="ecspresso.yml"  config file
  --debug                   enable debug log
  --envfile=ENVFILE ...     environment files
  --color                   enable colored output
  --output=table            output format (table|json|tsv)
  --revision=REVISION       revision number to output task definition as JSON