Make Request mutable

AppleLibs/Network/Requests/Request.swift

@@ -63,13 +63,13 @@ public class Request: CustomStringConvertible
         case delete = "DELETE"
     }
 
-    public let url: String
-    public let method: RequestMethod
-    public let authentication: Authentication?
-    public let parameters: [String: String]
-    public let payload: Data?
+    public var url: String
+    public var method: RequestMethod
+    public var authentication: Authentication?
+    public var parameters: [String: String]
+    public var payload: Data?
 
-    public let contentType: String?
+    public var contentType: String?
 
     public init(url: String, method: RequestMethod, authentication: Authentication?, parameters: [String: String] = [:], payload: Data? = nil, contentType: String?) {
         self.url = url