411 Length Required Error on some sites

Hi,

Using the latest node-spdyproxy version (`0.2.4`) is causing a `411 Length Required` nginx error on some sites.

Sample site: http://gorillavid.in/ or http://nodejs.org/

Request Headers:
```
GET http://gorillavid.in/ HTTP/1.1
:host: gorillavid.in
accept-charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3
accept-encoding: gzip,deflate,sdch
accept-language: de-DE,de;q=0.8,en-US;q=0.6,en;q=0.4
user-agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.31 (KHTML, like Gecko) Chrome/26.0.1410.63 Safari/537.31
:path: /
accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
:version: HTTP/1.1
cache-control: max-age=0
cookie: aff=1658
:scheme: http
:method: GET
```

Response Headers:
```
HTTP/1.1 411 OK
status: 411
version: HTTP/1.1
content-length: 576
content-type: text/html
date: Wed, 29 May 2013 17:47:43 GMT
proxy-agent: SPDY Proxy 0.2.4
server: nginx
```

Proxy output:
```
127.0.0.1:39678 - GET - stream ID: 1 - priority: 0
GET /
 > host: gorillavid.in
 > path: /
 > accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
 > accept-charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3
 > accept-encoding: gzip,deflate,sdch
 > accept-language: de-DE,de;q=0.8,en-US;q=0.6,en;q=0.4
 > cache-control: max-age=0
 > cookie: aff=1658
 > user-agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.31 (KHTML, like Gecko) Chrome/26.0.1410.63 Safari/537.31
 > transfer-encoding: chunked
```

Thanks.