fix(ntlm authentication)

[chimurai]

fix #39 - proxy ntlm authentication

_stream_writable.js:361
  cb();
  ^

TypeError: cb is not a function
    at afterWrite (_stream_writable.js:361:3)
    at onwrite (_stream_writable.js:352:7)
    at WritableState.onwrite (_stream_writable.js:89:5)
    at Socket._writeGeneric (net.js:714:5)
    at Socket._write (net.js:724:8)
    at doWrite (_stream_writable.js:307:12)
    at writeOrBuffer (_stream_writable.js:293:5)
    at Socket.Writable.write (_stream_writable.js:220:11)
    at Socket.write (net.js:650:40)
    at ClientRequest.OutgoingMessage._writeRaw (_http_outgoing.js:167:23)

[coveralls]

Coverage remained the same at 96.97% when pulling 58910af on fix-ntlm into 8689cb4 on master.

[coveralls]

Coverage remained the same at 96.97% when pulling 58910af on fix-ntlm into 8689cb4 on master.

[coveralls]

Coverage remained the same at 96.97% when pulling 58910af on fix-ntlm into 8689cb4 on master.