value_decode method should return a UTF-8 encoded string in ruby 1.8.
BTW, If you merge this PR, It seems that we'll merge PR #277 too.
The behavior of value_decode method is difference between ruby 1.8 an…
…d ruby 1.9. It should return a UTF-8 encoded string.
This is what I want!
I believe it's necessary just for 1.8 environment.
(since Ruby18.b_value_decode throws away the original encoding embedded in RFC 2047 encoded-word)
Thank you very much, this is great work. Merged