TMail not Ruby 1.9.2 compatible

[aselder]

In quoting.rb #is_binary_data? is called on a string.

Looking at http://apidock.com/ruby/String/is_binary_data%3F

it appears that this method was removed in Ruby 1.9.2

(This method is deprecated or moved on the latest stable version. The last existing version (v1_9_1_378) is shown here.)