Download data from OSF for testing

[eurunuela]

Closes #44 .

Changes proposed in this pull request:

• Remove data directory.
• Download data from OSF to perform tests.

[eurunuela]

So, in main we were using different mixing matrices for the integration and unit tests, which was confusing when working on this PR. I have removed duplicates so that there is only one mixing matrix for testing and have updated other benchmark files accordingly.

I think this is now ready to be merged. What do you think @tsalo ?

[codecov-commenter]

Codecov Report

Merging #45 (b561bdb) into main (82f281c) will not change coverage.
The diff coverage is 90.90%.

@@           Coverage Diff           @@
##             main      #45   +/-   ##
=======================================
  Coverage   63.15%   63.15%           
=======================================
  Files           7        7           
  Lines         418      418           
=======================================
  Hits          264      264           
  Misses        154      154           

Impacted Files	Coverage Δ
aroma/features.py	93.82% <83.33%> (ø)
aroma/utils.py	90.34% <100.00%> (ø)

[tsalo]

LGTM!