OkHttps 請求方法（GET|POST|PUT|DELETE）

　　同步與異步的HttpTask都擁有get、post、put與delete方法。不同的是：同步HttpTask的這些方法返回一個HttpResult，而異步HttpTask的這些方法返回一個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();     // 異步 GET
HttpCall call2 = http.async("/users").post();    // 異步 POST
HttpCall call3 = http.async("/users/1").put();   // 異步 PUT
HttpCall call4 = http.async("/users/1").delete();// 異步 DELETE