(Rails 5) 0.2.6 causes bundle conflict due to activesupport < 5.0 dependency

[wrburgess]

I'm unable to update the gem 5.2.6 version due to this line in the gemspec:

s.add_runtime_dependency 'activesupport', '< 5.0', '>= 3.0'

This seems to have been changed between commits bb6c7ba and
9deae35

Using rails 5.0.0.1 on bundle update, I'm getting this error:

airborne (= 0.2.6) was resolved to 0.2.6, which depends on
      activesupport (< 5.0, >= 3.0)