Go Http Ntlm Versions Save

• retry empty ntlm http header
• add challenge message validation

• Fix Build error on 32-bit systems because of int overflow (#16 )

• Add CookieJar to NTLMTransport (#15)

send negotiate version flag, fix message size (#14)

Handle multiple WWW-Authenticate headers correctly #11

• generate safer negotiate message
• better handle negotiate flags to process extended session security when required