Convert to using GraphQL for GitHub API

[IanLee1521]

It would be better to convert our REST calls to the GitHub API over to using the GraphQL endpoints.

Apparently this is emoting that now has a python package we may be able to use:

• https://github.com/graphcool/python-graphql-client

Example:

• https://github.com/GSA/code-gov-stats-jupyter-notebook/blob/master/code-gov-github-stats.ipynb

[LRWeber]

GraphQL functionality has been added via #7