CI: Update CI pipeline

[barucden]

Just like in JuliaML/LIBLINEAR.jl#31

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.86%. Comparing base (c884df6) to head (dcdb4b1).
Report is 3 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #102      +/-   ##
==========================================
+ Coverage   87.98%   89.86%   +1.88%     
==========================================
  Files           6        6              
  Lines         283      306      +23     
==========================================
+ Hits          249      275      +26     
+ Misses         34       31       -3     

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[barucden]

I took the CI settings from LIBLINEAR.jl. Now, Codecov runs, and we also test x86 architectures.

The inclusion of x86 revealed a few tests that were too strict, so I added a tolerance there. Can you check, @ablaom, that it is all good?

[ablaom]

Looks good to me, thanks.