Add script description to README (#176)

Author: dsypniewski

README.md

@@ -1,4 +1,14 @@
 # pySwitchbot [![Build Status](https://travis-ci.org/Danielhiversen/pySwitchbot.svg?branch=master)](https://travis-ci.org/Danielhiversen/pySwitchbot)
 Library to control Switchbot IoT devices https://www.switch-bot.com/bot
 
+## Obtaining locks encryption key
+Using the script `scripts/get_encryption_key.py` you can manually obtain locks encryption key.
+
+Usage:
+```shell
+python3 get_encryption_key.py MAC USERNAME
+```
+Where `MAC` is MAC address of the lock and `USERNAME` is your SwitchBot account username, after that script will ask for your password.
+If authentication succeeds then script should output your key id and encryption key.
+
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