Add test for HttpRequest and HttpUrl, bring classes up to spec, change how headers are passed around

test/Typertext/Http/HttpRequest.test.js

@@ -1,5 +1,5 @@
 describe("Typertext.Http.HttpRequest", function() {
-    it("Exists", function() {
+    it("exists", function() {
         expect(typeof Typertext.Http.HttpRequest).toBe("function");
     });
 });

test/Typertext/Json/JsonResponse.test.js

@@ -0,0 +1,5 @@
+describe("Typertext.Json.JsonResponse", function() {
+    it("exists", function() {
+        expect(typeof Typertext.Json.JsonResponse).toBe("function");
+    });
+});