Fix processing lists of matrices (in data)

[jgabry]

Submission Checklist

• Run unit tests
• Declare copyright holder and agree to license (see below)

Summary

Fixes #296.

This fixes a problem where lists of matrices were being converted to arrays of the wrong dimensions.

@rok-cesnovar @bbbales2 I think this PR is doing the right thing but we should be careful with it because I rewrote a bunch of the code and if it introduces any additional mistakes in data processing that would be particularly bad. @rok-cesnovar Can you take a look at the code and @bbbales2 if you by any chance have any spare time could you try to break this?

Copyright and Licensing

Please list the copyright holder for the work you are submitting
(this will be you or your assignee, such as a university or company):
Columbia University

By submitting this pull request, the copyright holder is agreeing to
license the submitted work under the following licenses:

• Code: BSD 3-clause (https://opensource.org/licenses/BSD-3-Clause)

[bbbales2]

This looks good to me (tested a little and I checked the code) though the test thing seems to disagree. Do we need to restart them though? I clicked one of the errors and it didn't look like a related message though I didn't put much effort into digging down. I clicked restart test anyway. Presumably they'll just fail in 30 minutes again if there's an actual problem.

[jgabry]

Thanks @bbbales2. I just fixed a test that was failing so I think the checks should pass now.

@rok-cesnovar If you're not too busy can you glance at the code changes and see if you notice any potential problems? If you're too busy right now no worries this can wait a bit or I can ask someone else to take a look.

[codecov-commenter]

Codecov Report

Merging #302 into master will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #302   +/-   ##
=======================================
  Coverage   90.15%   90.15%           
=======================================
  Files          12       12           
  Lines        2427     2428    +1     
=======================================
+ Hits         2188     2189    +1     
  Misses        239      239           

Impacted Files	Coverage Δ
R/data.R	100.00% <100.00%> (ø)

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[rok-cesnovar]

Looks good to me.