align is slow
## Summary
align process is slow
## What is the current bug behavior?

(8 calls, `DataFrames` of 400×300 approx)
## What is the expected correct behavior?
It should be faster.
## Logs/Traceback
cProfiler output in full: [strain_report_dev.dat](/uploads/341bcabc6ec2278d196ca8d16dd19768/strain_report_dev.dat)
## Possible fixes
- Known issue with `pandas`, see e.g. https://stackoverflow.com/questions/17401197/how-to-speed-up-pandas-multilevel-dataframe-shift-by-group . It is not Cython optimised.
- Indexing is the culprit, also known issue with `pandas`, see https://stackoverflow.com/questions/53997424/why-is-pandas-indexing-so-slow-how-to-make-it-faster
- Try `numba`?
issue