`Transfer-Encoding` requires some unpacking. There are two main directions to consider: chunking and compression. See http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.6 for detail.

On the one, chunking/HTTP streaming is not yet supported in `spray-client`, despite being supported in the underlying `spray-can`. Nothing to do here.

On the other, compression can be achieved by intercepting the request pipeline before the `sendReceive` step and injecting arbitrarily many `encode(...)` directives. We could do this here as well, but it would take some massaging in the current pipeline to get it working right. As I see, request encoding is still a to-do for Newman, so this can remain unimplemented for now.

So, with both of those in mind, it seems right to also drop `Transfer-Encoding`.