Add support to HTTP proxy, fix issue #22

Add support to HTTP proxy, fix issue #22
Do you think an additional variable would cause awk to be slow or to crash?
If not, I think it is better to follow **the same behavior as a modern web browser does**.

I am sure what I am doing. What about your opinion? :smile:

By the way, some useful information:
No proxy: Partial path, `Host` header field is the hostname in connection.
Normal proxy: Full path, `Host` header field is the target hostname.
Transparent proxy: Partial path, `Host` header field is the target hostname.

Again, I said Google can tolerant malformed HTTP requests. However that is not a reason to send one. :persevere: