Fix bug where we send an extra newline character at the end of a multipa...

As per.

http://www.w3.org/Protocols/rfc1341/7_2_Multipart.html

There is only one newline/CRLF required before the final --boundary--, the second newline will be interpreted as data and appended to the payload.

I'm not sure if this is a platform specific issue as I have not tested this on windows. Perhaps it changes and should be a specific hex string for the newline delimiters?