Upgrade to libuv 0.10.7.

When testing against the workload "-d10 -t8 -c1024 --pipeline 512" on
Linux, the server would run out of available connections. When combined
with the connection resets (asynchronous closing of client socket),
libuv would previously exhibit a high CPU load and leave server sockets
in the CLOSE_WAIT state. This would keep the memory usage high until
the sockets timed out and closed. See issue joyent/node#5389.

This behavior is corrected in this version.
Ignore SIGPIPE signal to prevent server failure.