Update Curve Docs

[akleb]

Purpose

Make it clear how interpolation/lms is used and what the order you select means for the spline.

Type of change

• [ ] Bugfix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (non-backwards-compatible fix or feature)
• [ ] Code style update (formatting, renaming)
• [ ] Refactoring (no functional changes, no API changes)
• [x] Documentation update
• [ ] Maintenance update
• [ ] Other (please describe)

Testing

Checklist

• [x] I have run flake8 and black to make sure the code adheres to PEP-8 and is consistently formatted
• [ ] I have run unit and regression tests which pass locally with my changes
• [ ] I have added new tests that prove my fix is effective or that my feature works
• [x] I have added necessary documentation

[codecov[bot]]

Codecov Report

Merging #33 (4b19eda) into master (ee307fa) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #33   +/-   ##
=======================================
  Coverage   60.55%   60.55%           
=======================================
  Files           5        5           
  Lines        1610     1610           
=======================================
  Hits          975      975           
  Misses        635      635           

Impacted Files	Coverage Δ
pyspline/pyCurve.py	51.87% <ø> (ø)

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