adding create_promotion endpoint to gem
fixed a doc type
Merge pull request #8 from mattmueller/feature/add-create-promotion

Feature/add create promotion
Bumping version and updating CHANGELOG for v0.3.6
Merge branch 'release/v0.3.6'

* release/v0.3.6:
  Bumping version and updating CHANGELOG for v0.3.6
  fixed a doc type
  adding create_promotion endpoint to gem