Expanding test suite

[ifilot]

• Test generation of .obj files
• Test generation of .stl files
• Test generation of .cub files
• Test reading of .cub files

[codecov-commenter]

Codecov Report

Merging #8 (af68f4e) into master (9aa1e6e) will increase coverage by 2.98%.
The diff coverage is 0.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master       #8      +/-   ##
==========================================
+ Coverage   40.75%   43.73%   +2.98%     
==========================================
  Files           5        5              
  Lines        1163     1166       +3     
  Branches      643      643              
==========================================
+ Hits          474      510      +36     
+ Misses        213      142      -71     
- Partials      476      514      +38     

Files	Coverage Δ
src/isosurface_mesh.cpp	29.16% <0.00%> (+1.19%)	⬆️

... and 1 file with indirect coverage changes