Log Message:
ruby-jirametrics: update to 2.8. Changes:

The main focus of this release is improving the experience with better
error messages, and more helpful suggestions.

- Bug: It wasn't possible to clear the description or title texts on
  individual charts.
- Added first_time_label_added for determining start or end times.
- Moved the generated timestamp of the report to the footer.
- Added the version number of JiraMetrics to the footer so there's
  a record of what version of the tool was used for this
  particular report.
- no_earlier_than previously only worked during the download stage and
  this proved to be confusing as there was no effect when just doing an
  export. It now works at both points and should be clearer as to what
  is actually happening.
- All the methods like first_time_in_status used to return a Time object
  and now return the ChangeItem that happened at that time. Unless
  you're writing your own methods, you likely won't even be aware that
  anything changed here. If you are, then you'll get a warning when
  returning a Time. The reason for this change is to give more context
  that will be useful in future reporting.
- Bug: We've discovered that Jira allows for multiple statuses with the
  same name and when this happens, it broke some of our existing logic.
  Fixes for this case have been added.
  - In standard_project, when specifying status_category_mappings, it's
    now possible to specify the ID at the same time as the name.
    "Review" will continue to specify just the name and \ 
"Review:4" will
    specify the name and also an ID of 4.
  - Status ID's are now mandatory and the tool will do it's best to
    guess the correct one, however it won't be able to guess in every
    case and you'll now get a error when it can't.
- Bug: some status category logic was failing in non-English instances
  of Jira because we were relying on category names, rather than keys.
  We think we've caught all the cases of this.