imap-backup.gemspec in imap-backup-5.0.0 vs imap-backup.gemspec in imap-backup-5.1.0

@@ -25,9 +25,10 @@
   gem.add_runtime_dependency "highline"
   gem.add_runtime_dependency "mail"
   gem.add_runtime_dependency "os"
   gem.add_runtime_dependency "rake"
   gem.add_runtime_dependency "thor", "~> 1.1"
+  gem.add_runtime_dependency "thunderbird", ">= 0.0.0"
 
   gem.add_development_dependency "aruba", ">= 0.0.0"
   gem.add_development_dependency "codeclimate-test-reporter", "~> 0.4.8"
   if RUBY_ENGINE == "jruby"
     gem.add_development_dependency "pry-debugger-jruby"