Another tryings on getting pointer done

With the help of rust IRC channel (thank you @bstrie and others!) I finally realized that current rust-http
state (requires request headers change for posting) doesn't allows me to re-use RequestWriter in Graph struct
without memory issues in consequences, so it's actually not a big deal to create a new RequestWriter for each
request (since it supposed to go out from memory after use), at least until teepee will give a better solution.
Also see issue #121 in rust-http.