Do not buffer the entire package in memory

[lowjoel]

Faraday currently does not support streaming responses (lostisland/faraday#45, lostisland/faraday#156, lostisland/faraday#363, lostisland/faraday#461, lostisland/faraday#522). This means that the entire package must be buffered in memory.

This is okay for the majority of packages, but not for excessively large ones (> 50mb?)