Fix Ruby 2.2 build

Author: mshibuya

Appraisals

@@ -6,6 +6,7 @@ appraise "rails-5.0" do
   group :test do
     gem 'cancancan', '~> 2.0'
     gem 'paperclip', ['>= 3.4', '!= 4.3.0']
+    gem 'mimemagic', '< 0.3.10'
     gem 'shrine', '~> 2.13.0'
     gem 'shrine-memory'
   end

gemfiles/rails_5.0.gemfile

@@ -49,6 +49,7 @@ group :test do
   gem "timecop", ">= 0.5"
   gem "tzinfo-data", platforms: [:mingw, :mswin, :x64_mingw, :jruby]
   gem "paperclip", [">= 3.4", "!= 4.3.0"]
+  gem "mimemagic", "< 0.3.10"
   gem "shrine", "~> 2.13.0"
   gem "shrine-memory"