Consider adding preconfigured Matrix client

matrix.org requires users to sign up for an account, something we don't really want. We want guests to be allowed, just like on IRC.

https://github.com/matrix-org/matrix-python-sdk is straightforward, BUT showstopper: `Guest access not allowed` for IRC bridged channels?

```
>>> from matrix_client.client import MatrixClient
>>> client = MatrixClient("http://matrix.org")
>>> token = client.register_as_guest( )
>>> token = client.register_as_guest()
>>> print(token)
...-...
>>> room = client.join_room("#freenode_#hellosystem:matrix.org")
Traceback (most recent call last):
File "", line 1, in
File "/tmp/matrix-python-sdk/matrix_client/client.py", line 337, in join_room
response = self.api.join_room(room_id_or_alias)
File "/tmp/matrix-python-sdk/matrix_client/api.py", line 234, in join_room
return self._send("POST", path)
File "/tmp/matrix-python-sdk/matrix_client/api.py", line 749, in _send
code=response.status_code, content=response.text
matrix_client.errors.MatrixRequestError: 403: {"errcode":"M_FORBIDDEN","error":"Guest access not allowed"}
```