v0.6.0

• Added: Redmine.auth() shortcut for the case if we just want to check if user provided
  valid auth credentials, can be used for user authentication on external resource based on
  Redmine user database (see docs for details)
• Fixed: JSONDecodeError was raised in some Redmine versions during some create/update
  operations (thanks to 0x55aa)
• Fixed: User resource status attribute was converted to IssueStatus resource by mistake