Rate limit threshold and wait time reconfigured

Rate limit threshold changed to max 99 percent
Wait time changed from 170s to 3600s

Update for API version 7.0

Updated routing for API call to apply for V7.0

Update for API version 3.3

1. Updated the API request route in request-lib.py
2. Shortened wait per request time to 0.6s and wait time per ~50 requests to 170s

Add checkpoint update feature

fix previous checkpoint update issue for new category
now, the country_start will update to 0 after all the countries for 1 category completed GET requests

First release of request_lib for Facebook Marketing API

1.0

Update README.md