Improve CLI help output

[Turbo87]

lerna-changelog [options]

Optionen:
  --help      Hilfe anzeigen                                                               [boolean]
  --version   Version anzeigen                                                             [boolean]
  --tag-from  A git tag that determines the lower bound of the range of commits (defaults to last
              available)                                                                    [string]
  --tag-to    A git tag that determines the upper bound of the range of commits             [string]

Beispiele:
  lerna-changelog                                  create a changelog for the changes after the
                                                   latest available tag
  lerna-changelog --tag-from 0.1.0 --tag-to 0.3.0  create a changelog for the changes in all tags
                                                   within the given range

For more information, see https://github.com/lerna/lerna-changelog