build test suite for `/tasks` API endpoint

[MarchandMD]

• Currently, there is no test suite for the /tasks endpoint
• Jest and SuperTest have been installed
• Test the endpoints for accuracy
  • GET /tasks
  • GET /tasks/:id
  • POST /tasks
  • PATCH /tasks/:id
  • DELETE /tasks/:id

(could be broken into multiple user stories)

[l-e-u]

I have the other suites covered, if you want I can take this one off your hands too.