begin refactor of proxy engine

proxychain/rqm/spoof_user_agent.go

@@ -0,0 +1,13 @@
+package rqm // ReQuestModifier
+
+import (
+	"ladder/proxychain"
+)
+
+// SpoofUserAgent modifies the user agent
+func SpoofUserAgent(ua string) proxychain.RequestModification {
+	return func(px *proxychain.ProxyChain) error {
+		px.Request.Header.Set("user-agent", ua)
+		return nil
+	}
+}