Matt updats to SRR and CODS

[noromo01]

Matt’s updates to SRR algorithm (detect negative shifts in soiling ratio and fit multiple soiling rates per soiling interval (piecewise)) as well as CODS algorithm being added

• [ ] Code changes are covered by tests
• [ ] Code changes have been evaluated for compatibility/integration with TrendAnalysis
• [ ] New functions added to __init__.py
• [ ] API.rst is up to date, along with other sphinx docs pages
• [ ] Example notebooks are rerun and differences in results scrutinized
• [ ] Updated changelog

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 73.68421% with 90 lines in your changes missing coverage. Please review.

Project coverage is 72.80%. Comparing base (bb24f06) to head (9e3a411).

Files	Patch %	Lines
rdtools/filtering.py	65.74%	62 Missing :warning:
rdtools/analysis_chains.py	83.22%	26 Missing :warning:
versioneer.py	0.00%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## development #417 +/- ## =============================================== - Coverage 73.88% 72.80% -1.09% =============================================== Files 13 13 Lines 2711 2982 +271 =============================================== + Hits 2003 2171 +168 - Misses 708 811 +103 ```

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