This is no longer compatible with the docker version of home assistant

When the Home Assistant moved to being based on Arch Linux it no longer included support for curl with ldap or ldapsearch. This can be solved by creating a custom docker build with the following docker file to add support for ldapsearch:


```
FROM homeassistant/home-assistant:stable
RUN apk add openldap-clients
```

Might be worth adding a note about this to the readme.