This project is using a minimal API version of version 23. The required minimal version is 21, however that was not realized before it was too late. No API 23 specific features are used, however downgrading to version 21 ruines the project. Since the app is only supposed to follow with a tablet from the client's clients, it is not the highest priority to downgrade to API 21.
This project now has a minimal SDK version of API 21. All tests are runned on API 25 using Circle CI.