Update http_parser to support PATCH method

This commit solve the issue #157. Here's the output:

```
$ ruby custom_server.rb -sv 
[6663:INFO] 2013-06-18 10:59:02 :: Starting server on 0.0.0.0:9000 in development mode. Watch out for stones.
[6663:INFO] 2013-06-18 11:03:28 :: Status: 200, Content-Length: 6, Response Time: 2.60m
```

```
$ curl -X PATCH -v http://localhost:9000/example -d 'data={"example":true}'
* Adding handle: conn: 0x2115d90
* Adding handle: send: 0
* Adding handle: recv: 0
* Curl_addHandleToPipeline: length: 1
* - Conn 0 (0x2115d90) send_pipe: 1, recv_pipe: 0
* About to connect() to localhost port 9000 (#0)
*   Trying ::1...
* Connection refused
*   Trying 127.0.0.1...
* Connected to localhost (127.0.0.1) port 9000 (#0)
> PATCH /example HTTP/1.1
> User-Agent: curl/7.30.0
> Host: localhost:9000
> Accept: */*
> Content-Length: 21
> Content-Type: application/x-www-form-urlencoded
> 
* upload completely sent off: 21 out of 21 bytes
< HTTP/1.1 200 OK
< Content-Length: 6
* Server Goliath is not blacklisted
< Server: Goliath
< Date: Tue, 18 Jun 2013 04:03:28 GMT
< 
* Connection #0 to host localhost left intact
hello!
```