node v6.8.0 supports a `timeout` option now, so we should
explicitly delete it in case the value is < 0 (in which case
node will throw an error). Handling timeouts manually for now
is better for consistency with older node versions.

Prior to this commit, the connection timeout could include some
amount of time that passes before the socket actually starts its
connection attempt.

Additionally, this commit only starts the request timeout once a
connection is made. This helps to prevent an issue where one kind of
timeout is seen instead of another (ETIMEDOUT vs ESOCKETTIMEOUT)
while connecting in some situations (depending on OS and possibly
node version).