* Basic fix for issue: https://github.com/python-kasa/python-kasa/issues/373
Change usage module get_daystat and get_monthat to return dictionaries of date index: time values as spec'd instead of raw usage data. Output matches emeter module get_daystat and get_monthstat
* Fixed some formatting and lint warnings to comply with black/flake8
Use the new _convert function in emeter for all conversions rather than the one in smartdevice.py
Removed unused function _emeter_convert_emeter_data from smartdevice.py
* Added a first pass test module for testing the new usage conversion function
* Changes based on PR feedback
Tidied up some doc string comments
Added a check for explicit values from conversion function
* Rebase on top of current master, fix docstrings
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Co-authored-by: Teemu Rytilahti <tpr@iki.fi>
