Move resampler out of parsers, remove relative paths for import

[alisnwu]

closes #138

All discussions made in #158 and #163

@sbillinge Ready for review

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.17%. Comparing base (e9a7b2d) to head (ccecf10).
Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #164   +/-   ##
=======================================
  Coverage   99.17%   99.17%           
=======================================
  Files           7        7           
  Lines         242      243    +1     
=======================================
+ Hits          240      241    +1     
  Misses          2        2           

Files with missing lines	Coverage Δ
tests/test_loaddata.py	97.77% <100.00%> (ø)
tests/test_resample.py	94.73% <100.00%> (ø)
tests/test_serialization.py	100.00% <100.00%> (ø)