Started work on an issues-based backend.
Started stubbing out tests for the issues backend.
Fixed the tests so they properly fail.
Started with issue based comments.
Finished initial draft for issues.
Added cache clearing to afterEach for the tests.
Refactored most of the duplicated code into more generic functions.

Minor code styling fixes.
Updated README and simplified configuration of the gist/issue mappings.
Fixed the tests after the change to CONFIG.MAPPINGS.
Fixed code styling issues.