Add support to HTTP proxy, fix issue #22

Add support to HTTP proxy, fix issue #22
Yes, I've definitely read those RFC docs :alien:, all it says is what a transparent proxy "must not" do:

> A transparent proxy MUST NOT rewrite the "abs_path" part of the received Request-URI when forwarding it to the next inbound server, except as noted above to replace a null abs_path with "/".
>
>      Note: The "no rewrite" rule prevents the proxy from changing the
>      meaning of the request when the origin server is improperly using
>      a non-reserved URI character for a reserved purpose.  Implementors
>      should be aware that some pre-HTTP/1.1 proxies have been known to
>      rewrite the Request-URI.

Surely I have no idea **how non-transparent proxies work** (correct me if I'm wrong since I'm not really good at this and I have no experience on implementing proxies :frowning: ); but isn't your original request line (say, if you are on an anonymous proxy, like Privoxy)

```
GET /translate_a/t?client=t HTTP/1.1
```
forwarded as:
```
GET http://translate.google.com/translate_a/t?client=t HTTP/1.1
```
? (again, I have no knowledge on this, just curious about how non-transparent proxy handles it)