Passes unicode strings to rtfng instead of utf-8 bytestrings. 

This should fix non-ASCII characters in the RTF export.

This has only been tested locally by me, not on the production data, but it looks like it ought to work. :) I'm also not sure how well any given RTF program will interoperate with what rtfng produces, but this works for me on OSX 10.9.2's TextEdit and ®.

@dianaclarke indicated that this was broken e.g. for "Rackspace®", if you check the diamond sponsor RTF export.

Let me know if I can provide more help on this. Thanks!