Added nested routing for calls in cycles

These routes now work

• /cycles
• /cycles/1
• /cycles/1/calls
• /calls
• /calls/1

Tests were added using pytest, factory-boy is used for generating test data nicely (the project was setup to use these).

Two distinct folders in the project:

• api - contains simple 'smoke' tests for api endpoints, for every end point it tests basic http status code and a test payload
• unit - to contain actual logic and function tests, nothing here yet