Configurable temporary file location

Hey Nathan,

Just made a tweak to the multipart uploader so it let's you configure the temporary folder location (falls back to `os.tmpDir()` if none specified).

Additionally, just a few syntax tweaks that jshint was nagging me about.

Also, I reckon this module deserves at least a 0.1.x status :)

Have a good weekend!

Cheers,
Damon.