unittest for tmpo-py

[saroele]

Although the tmpo-py library seems to do what it should, I propose to create a unittest for it. We will rely entirely on this library to get our data, so reliability is important.

I would personally go for a mix between a unittest and an integration test, meaning I don't want to mock the local tmpo database. @icarus75 can we make a specific version of the local database for testing, with just a couple sensors and a tiny bit of data? This database should be part of the repo so everyone can run the test on his own pc.