docs: README 中的错误示例

用 asyncio 的形式改写

.gitignore

@@ -60,7 +60,7 @@ target/
 site
 
 # commitizen
-package.json
+# package.json
 node_modules
 
 # venv

README.md

@@ -52,28 +52,26 @@ $ python -m ramjet [--debug=true]
 ### 异步
 
 ```py
+import random
+import asyncio
+
 from ramjet.engines import process_executor, thread_executor, ioloop
 
 
 def bind_task():
     # 将任务添加进事件循环中
-    ioloop.add_future(async_task(), callback)
-
-
-@tornado.gen.coroutine
-def async_task():
-    yield tornado.gen.sleep(3)
-    yield async_child_task()
+    asyncio.ensure_future(async_task())
 
 
-@tornado.gen.coroutine
-def async_child_task():
-    yield tornado.gen.sleep(1)
-    print('child task ok!')
+async def async_task():
+    await asyncio.sleep(3)
+    for i in range(10):
+        asyncio.ensure_future(async_child_task(i))
 
 
-def callback(future):
-    print('ok')
+async def async_child_task(n):
+    await asyncio.sleep(random.random())
+    print('child task {} ok!'.format(n))
 
 ```
 
@@ -104,14 +102,13 @@ from ramjet.engines import process_executor, thread_executor, ioloop
 
 
 def bind_task():
-    now = ioloop.time()
-    run_at = now + 3600
-    ioloop.call_at(run_at, task, your_auguments)
+    delay = 3600
+    ioloop.call_later(delay, task, your_auguments)
 
 
 def task(*args, **kw):
     # 可以在 task 内设置下一次执行的时间
-    # ioloop.run_at(run_at, task, *args, **kw)
+    # ioloop.call_later(delay, task, *args, **kw)
 ```
 
 ## Versions

package.json

@@ -0,0 +1,26 @@
+{
+  "name": "ramjet",
+  "version": "1.0.0",
+  "description": "Ramjet ===",
+  "main": "index.js",
+  "directories": {
+    "test": "tests"
+  },
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git@git01.dds.com:ops/ramjet.git"
+  },
+  "author": "",
+  "license": "ISC",
+  "devDependencies": {
+    "cz-conventional-changelog": "^1.1.6"
+  },
+  "config": {
+    "commitizen": {
+      "path": "./node_modules/cz-conventional-changelog"
+    }
+  }
+}