Refactor to remove superfluous usage of x_id and x.id
Require user authentication.
Refactor to prevent non-admins from editing plant varieties.
Refactor to enforce admin authorization. Resolves #44
Switch to using poltergeist as the default.
Merge branch 'master' into add-shapes-to-garden-plan

* master:
  Switch to using poltergeist as the default.
  Refactor to enforce admin authorization. Resolves #44
  Refactor to prevent non-admins from editing plant varieties.
  Require user authentication.
  Refactor to remove superfluous usage of x_id and x.id