Merge back PR248 onto develop

[israelmcmc]

This code by @Yong2Sheng has already been reviewed in #248. I rebased it onto the v0.3.x branch, and merged through #350. I was planning to merge it onto develop right after v0.3 was released, but I forgot.

I'm opening this PR for our records, and to make sure the tests are passing. I'll merge it right after, no need to review it again.

[codecov]

Codecov Report

❌ Patch coverage is 33.33333% with 82 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.78%. Comparing base (22abd1c) to head (b4166f6).
⚠️ Report is 9 commits behind head on develop.

Files with missing lines	Patch %	Lines
cosipy/ts_map/moc_ts_fit.py	22.33%	80 Missing ⚠️
cosipy/ts_map/fast_ts_fit.py	88.23%	2 Missing ⚠️

❌ Your patch status has failed because the patch coverage (33.33%) is below the target coverage (100.00%). You can increase the patch coverage or adjust the target coverage.

Files with missing lines	Coverage Δ
cosipy/__init__.py	100.00% <100.00%> (ø)
cosipy/ts_map/__init__.py	100.00% <100.00%> (ø)
cosipy/ts_map/fast_ts_fit.py	89.61% <88.23%> (-0.39%)	⬇️
cosipy/ts_map/moc_ts_fit.py	22.33% <22.33%> (ø)

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.