Refactor ShowBreadcrumb implementation and specs.

Switch to modern "expect" syntax for rspec in the specs. Rename
`lookup_breadcrumbs` to `collect_crumbs` to better explain what it does.

[8212]
Update gemspec author and added ActiveSupport and ActiveRecord as dependencies.
Update has_breadcrumb to modern syntax and to be self documenting.

Started using in file classes to document the usage of the
has_breadcrumb method so that you can see it and understand right there
instead of using the packaged models. Cut those specs run time by 80%
and improved understanding when reading the tests.

[8212]