Integrate Slice schedules with Pi users

[pmanko]

Overview

Slice will serve as the backend application for creating, assigning, and managing Pi user surveys and questionnaires.

Implementation

• Slice and Pi will communicate using JSON objects.
• Pi will interact with Slice as a user, and will have one corresponding project in Slice that houses all of the patient data.
• Upon initialization of a new user in Pi, a new, corresponding subject will be created in Slice.
• Users will be assigned surveys and questionnaires (designs) in Slice using schedules.
• Schedules also contain links to completed sheets, and time information for when a given design is assigned.
• Pi will present the user with a simplified view of all of this information, bringing together information on assigned designs, completed sheets, degree of completion, assignment dates, overdue status, etc. into a simple and clear
  interface.

[pmanko]

Trying out connecting to slice using the method in the send_message function from https://github.com/remomueller/screen/blob/master/app/controllers/application_controller.rb but keep getting HTTP 422 unprocessable entity error