fix: explicitly require mime-types 2.99 to keep Ruby 1.9.x compatibility

1.9 is EOL, so we probably should follow along asap.

Author: rmehner

transloadit.gemspec

@@ -24,7 +24,7 @@ Gem::Specification.new do |gem|
 
   gem.add_dependency 'rest-client'
   gem.add_dependency 'multi_json'
-  gem.add_dependency 'mime-types'
+  gem.add_dependency 'mime-types', '~> 2.99'
 
   gem.add_development_dependency 'rake'
   gem.add_development_dependency 'minitest'