Replace einder lib with horimote

[benleb]

Description:

Unitymedia Germany changed the port and XML filename which is used by the horizon component to check the online/available state. As the original maintainer of the used einder lib does not want to maintain it anymore (i talked to him, he does also not use it anymore), it is replaced by horimote. Horimote is a einder fork with updated port and filename.

Related issue (if applicable): Horizon cannot detect state and allows no device control.

Checklist:

• The code change is tested and works locally.
• Local tests pass with tox. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated in home-assistant.io

If the code communicates with devices, web services, or third-party tools:

• New dependencies have been added to the REQUIREMENTS variable (example).
• New dependencies are only imported inside functions that use them (example).
• New or updated dependencies have been added to requirements_all.txt by running script/gen_requirements_all.py.
• New files were added to .coveragerc.

If the code does not interact with devices:

• Tests have been added to verify that the new code works.

[cgtobi]

LGTM