lib/mms2r/media.rb
def type_from_filename(filename)
      ext = filename.split('.').last
      ent = MMS2R::EXT.detect{|k,v| v == ext}
      ent.nil? ? nil : ent.first
    end
def type_from_filename(filename)
      ext = filename.split('.').last
      ent = MMS2R::EXT.detect{|k,v| v == ext}
      ent.nil? ? nil : ent.first
    end
guess content type from filename