Some fixes for daemon

It makes it use `data_files` in `setup.py` and replaces tests for `powerline-client` with tests for `powerline` (should be useless though as it is always being installed). First is not the best fix as it does not work with `pip install -e`, only without `-e`.

I guess you should not merge this directly (for this violating gitflow), but instead pull+merge --ff-only.