Refactor to atomic transforms + data sources

[mheap]

This refactor adds the following:

• Unit tests to be written for all of the transforms
• Allows all transforms to be skipped
• Switch to the debug module for logging
• Replacements may now use an async function to fetch data before returning the required replacements

Known gaps:

• Octokit enterprise functionality unit tests
• updateContent tests

There are BREAKING CHANGES to the CLI interface, and so this must be released as a v2.