This reverts commit 5e2612c.

There seems to be problems with this, causing non-stalled uploads to
report timeouts as well. Need to investigate.

This patch introduces two new events to the multipart parser:
'onHeaderEnd' and 'onHeadersEnd'. These make it much easier to properly
handle the output of the parser.

Another nice addition is a system test that verifies a complete upload
from start to finish.

The parser is now considered safe. A malicious client can no longer
allocate huge amounts of memory by sending a big field.