Logic for fetching and saving all pull request related data
Logic for fetching and saving all pull request related data

Creates public method `fetch_and_save!` that will ultimately:

- get all merged pull requests, for all our repos
- get all commits for those pull requests

Then calls for the organization of that data into a common, savable format, and saves it to the database as:

- GitHubStatistic records
- GitHubUser records

Smartly hits GitHub’s API for records that have been merged since the last record we have in our db, as well as only saving records to our db that do not already exist.

OperationCode/operationcode_backend,OperationCode/operationcode_backend,OperationCode/operationcode_backend