Get APY results from backend endpoint

[michalsmiarowski]

Depends on https://github.com/keep-network/website-backend/pull/17

Get APY result from the website-backend instead of counring it on the frontend.

Steps to run it locally:

1. website-backend: go to the /calculate-apy route in flask.py and change line

   @cross_origin(origins=re.compile('https://(.+\.)?keep\.network'))

   to

   @cross_origin(origins=http://localhost:<host_number_of_the_frontend_app'))

   Rebuild and rerun the docker image after (you will probably have to also remove the current image before reruning it)

2. Frontend app: Got to redux.js and change API_URL variable to:

   export const API_URL = "http://localhost:<host_number_of_the_backend_app>"