Allow specifying what fixtures can be ignored by setting
`ignore` in fixtures YAML file:
# users.yml
_fixture:
ignore:
- base
base: &base
admin: false
introduction: "This is a default description"
admin:
<<: *base
admin: true
visitor:
<<: *base
In the above example, "base" fixture will be ignored when creating
users fixture. This is helpful when you want to inherit attributes
and it makes your fixtures more "DRY".
