#18 limit streaming loading into memory

[Daniel Mealha Cabrita]

Currently, while loading a streaming to memory (because Ziproxy thinks it's worth processing) it does not check it against MaxSize.

The big problem with this is there are some HTTP sites which claims that things like an ISO image are text. In such cases Ziproxy will try to load the whole 650MB (or more) data into memory before doing anything else.

This bug may also be used for DoS, if the user commands a huge file to be loaded and the server runs out of memory.