human validation of computed version should be optional

[FrancescoCioria]

user story

as a user I would like to be able to use smooth-release to automatically release a version from a CI task

requirements

after the npm-version task, smooth-release always asks the user to confirm the computed version.
This step should be optional as everything else

specs

• add config parameter publish.npmVersionConfirmation
  • defaults to true so not be breaking
• avoid confirmation step if publish.npmVersionConfirmation is false

misc

{optional: other useful info}