String SignUpURl = base + "users/add.json?"
                + "first_name=" + fname_str + "&last_name=" + lname_str
                + "&username=" + email_str + "&password=" + password_str;
HttpContext mHttpContext = new BasicHttpContext();
HttpPost mHttpPost = new HttpPost(SignUpURl);
mHttpClient.execute(mHttpPost, mHttpContext);