Update blog_article active_support requires. Fixes #205

As far as I can tell, requiring `activesupport/core_ext/time/acts_like` keeps us from taking a bad branch at https://github.com/rails/rails/blob/master/activesupport/lib/active_support/core_ext/date_and_time/zones.rb#L21 which leads to an exception when [calling `to_time` with a parameter](https://github.com/rails/rails/blob/master/activesupport/lib/active_support/core_ext/date_and_time/zones.rb#L36).

I wonder, though, if it might be easier just to include all the ActiveSupport Time `core_ext`s rather than cherry-pick at this granularity.