同步与异步的HttpTask都拥有get、post、put与delete方法。不同的是：同步HttpTask的这些方法返回一个HttpResult，而异步HttpTask的这些方法返回一个HttpCall。

HttpResult res1 = http.sync("/users").get();     // 同步 GET
HttpResult res2 = http.sync("/users")post();     // 同步 POST
HttpResult res3 = http.sync("/users/1").put();   // 同步 PUT
HttpResult res4 = http.sync("/users/1").delete();// 同步 DELETE
HttpCall call1 = http.async("/users").get();     // 异步 GET
HttpCall call2 = http.async("/users").post();    // 异步 POST
HttpCall call3 = http.async("/users/1").put();   // 异步 PUT
HttpCall call4 = http.async("/users/1").delete();// 异步 DELETE