Implementing ability to track top k (-k, --top-stories-count) stories simultaneously
Previously, once a top story is being tracked, we do not store any information about the second, or third top stories. This is problematic because if the second top story becomes the new top story, we lose the early CCs for this story because they existed during the reign of the initial top story.
This phenomena can be explained by the sequential layout of the lines (e.g., Fig. 1) which incorrectly implies that the second top news story (blue) line existed only after the first (red line) stopped.