Feature: add Jobs resource
This adds support for fetching jobs for each project, which is useful for analyzing CI performance, coverage changes, etc.
Because the issues API doesn't support ordering or date offsets, the state management is a little different here - we scan backwards until we find the first non-terminal job with a created_at older than start_date.
I also noticed Pipelines were missing from the README so I thew it in there, but I can do a separate PR for it if preferred.
Closes #28 (closed)