acts-as-taggable-on and Rails 5

Bundler could not find compatible versions for gem "activerecord":
  In snapshot (Gemfile.lock):
    activerecord (= 5.0.0)

  In Gemfile:
    acts-as-taggable-on (~> 3.4) was resolved to 3.4.0, which depends on
      activerecord (< 5, >= 3.2)

    rails (~> 5.0.0) was resolved to 5.0.0, which depends on
      activerecord (= 5.0.0)

Running `bundle update` will rebuild your snapshot from scratch, using only
the gems in your Gemfile, which may resolve the conflict.

Resolution:

gem 'acts-as-taggable-on', :git => 'https://github.com/mbleigh/acts-as-taggable-on'