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)