Close the original connection when we're done with it

I have no idea if this is actually the right fix or not, but the problem I am seeing is that (at least with node 0.10) failure to close the underlying connection when doing a redirect causes the timeout to fire, resulting in the failure of tests later on.

Similarly failing to close the connection when `asString` aborts because it finds a binary file causes a "socket hung up" exception at some later point.