An easy-to-use burndown chart generator for GitHub Project Boards.

Refactor -> use parameterized GraphQL query master

To make a cleaner separation between graphql and python code, this commit extracts the graphql query text from the api_wrapper module. Folders were restructured to facilitate the future addition of automated unit tests. Lastly, a Makefile was added to make it easier to build, test, and run the burndown chart generator.