#32 timeout bug

[Daniel Mealha Cabrita]

When it comes to data which is fully loaded into memory for processing
(pictures being the most usual case) Ziproxy is (wrongly) considering timeout
the whole elapsed time, instead of inactivity timeout.

The problem with this is when the picture takes too long to load (when link speed is terribly low, or when the picture is huge) it will timeout regardless the network activity.