Add location tests

[AurelienJaquier]

No description provided.

[AurelienJaquier]

It looks like I cannot add reviewers. @DrTaDa @arnaudon could you have a look at it please?

[codecov-commenter]

Codecov Report

Merging #403 (d5a31b6) into master (5f49d9f) will increase coverage by 0.77%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #403      +/-   ##
==========================================
+ Coverage   89.70%   90.47%   +0.77%     
==========================================
  Files          41       41              
  Lines        2457     2457              
==========================================
+ Hits         2204     2223      +19     
+ Misses        253      234      -19     

Impacted Files	Coverage Δ
bluepyopt/ephys/locations.py	95.08% <0.00%> (+15.57%)	⬆️

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[arnaudon]

thank you!