Fix ruby binary field encoding in TJSONProtocol

Ruby JSON protocol uses pack('m') method to encode Base64 string.
It seems that it inserts a "\n" character every 60 characters.

You can refer to these pages for this behavior.
http://stackoverflow.com/questions/2620975/strange-n-in-base64-encoded-string-in-ruby
http://ruby-doc.org/stdlib-2.2.3/libdoc/base64/rdoc/Base64.html

Line feeds are added to every 60 encoded characters.

This has been making it impossible to send long binary field data to other languages.
I fixed this by using alternative encode method that is added in Ruby 1.9 (which should be OK).

After the fix, I had to add Ruby namespace to DebugProtoTest.thrift to avoid name collision of "Base64" symbols that is used for new encode method and also as DebugProtoTest message name.

I also removed extraneous double quote in encoded binary fields that resulted in invalid JSON.