update README

Author: lyuwen

README.md

@@ -1,7 +1,37 @@
 # pyslack
 
-A python to slack interface. It is using Slack legacy tokens.
+A command line python base interface to Slack. It uses Slack New App API verion 2.0.
+
+## Install
+
+Create an App on slack and enable `chat:write`, `im:write` and `files:write` permissions.
+Install the app, and save the Bot User Token OAuth Access Token to `$HOME/.pyslackrc` from the template `pyslackrc.sample`. 
+And install the python package.
+
+
+``` bash
+python setup.py build && python setup.py install
+
+```
+
+**or**
+
+``` bash
+pip install .
+
+```
 
 ## Usage
 
-Copy pyslackrc.sample to `$HOME/.pyslackrc`. And run the program.
+* Send a text message.
+
+  ``` bash
+  pyslack text --channel #random  --text "This is a test message."
+  ```
+
+* Upload a file.
+
+  ``` bash
+  pyslack file --channel #random  --file /path/to/file --title FileTitle --filetype <file type> \
+    --initial-comment "This is the comment"
+  ```