Lua HTTP client cosocket driver for OpenResty / ngx_lua

Features:
- HTTP 1.0 and 1.1
- SSL
- Streaming interface to the response body, for predictable memory usage
- Alternative simple interface for single-shot requests without a manual
  connection step
- Chunked and non-chunked transfer encodings
- Connection keepalives
- Request pipelining
- Trailers
- HTTP proxy connections
