Fixed #50 - timestamps need to be int/long, not float.

Finally fixed properly this time.
Merge pull request #55 from jgeewax/datetime-fix-again

Fixed #50 - timestamps need to be int/long, not float.
Fixes #52 - Allow query-string authentication (aka, signing URLs).
Merge pull request #56 from jgeewax/signed-urls

Fixes #52 - Allow query-string authentication (aka, signing URLs).