Add support for http proxy (#68)

* Add support for http proxy

* add test case for http proxy

---------

Co-authored-by: octeep <github@bandersnatch.anonaddy.com>
Co-authored-by: pufferfish <74378430+pufferffish@users.noreply.github.com>

util.go

@@ -0,0 +1,25 @@
+package wireproxy
+
+import (
+	"bytes"
+	"io"
+	"net/http"
+	"strconv"
+)
+
+const space = " "
+
+func responseWith(req *http.Request, statusCode int) *http.Response {
+	statusText := http.StatusText(statusCode)
+	body := "wireproxy:" + space + req.Proto + space + strconv.Itoa(statusCode) + space + statusText + "\r\n"
+
+	return &http.Response{
+		StatusCode: statusCode,
+		Status:     statusText,
+		Proto:      req.Proto,
+		ProtoMajor: req.ProtoMajor,
+		ProtoMinor: req.ProtoMinor,
+		Header:     http.Header{},
+		Body:       io.NopCloser(bytes.NewBufferString(body)),
+	}
+}