Not compatible with Rails 5 - mongoid-fixture_set depends on activesupport ~>4.0

[vanboom]

Bundler could not find compatible versions for gem "activesupport":
In snapshot (Gemfile.lock):
activesupport (= 5.2.1)

In Gemfile:
mongoid-fixture_set was resolved to 1.5.0, which depends on
activesupport (~> 4.0)

rails (~> 5.2.1) was resolved to 5.2.1, which depends on
  activesupport (= 5.2.1)