requests are leaving open sockets?

Hi,

I have a program that performs several requests in a loop, with a 1 second sleep between them, and I noticed the number of open sockets in my process was growing. I modified it to run `garbagecollect()` after each request, and now the number of sockets is stable.

After a quick look at the sources, it wasn't clear to me how/where to fix this. (Perhaps it's a LuaSocket issue!?)

Thanks!
