using nan instread of None and updated tests

[sonelu]

Closes #57

[codecov]

Codecov Report

Merging #58 into master will increase coverage by 0.13%.
The diff coverage is 92.42%.

@@            Coverage Diff             @@
##           master      #58      +/-   ##
==========================================
+ Coverage   95.99%   96.12%   +0.13%     
==========================================
  Files          25       25              
  Lines        2248     2248              
  Branches      330      331       +1     
==========================================
+ Hits         2158     2161       +3     
+ Misses         57       55       -2     
+ Partials       33       32       -1     

Impacted Files	Coverage Δ
roboglia/base/joint.py	98.76% <89.65%> (-1.24%)	⬇️
roboglia/base/robot.py	97.45% <90.47%> (+0.38%)	⬆️
roboglia/base/bus.py	94.87% <100.00%> (ø)
roboglia/move/moves.py	98.27% <100.00%> (+1.72%)	⬆️
roboglia/base/thread.py	96.55% <0.00%> (+1.37%)	⬆️

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