[gem] add more code analysis gems. Cane, Roodi, Tailor.

Also get the `rake stats` report.
Merge branch 'metricks'
[preflight] use metriknit gem for most of the code metrics.
[CalendarController] include site name in meta description for actions.
[preflight] support `--git` for git-only processing on metrics.

When `preflight --git` is called, only the files with changes that are uncommitted in git will be included in the metriknit report.
[EventPresenter][CalendarMonthPresenter] apply css classes to cancelled and tentative events.
[gem] minor updates.

No code changes required

ZenTest 4.9.1
flog 4.0.0
etc.