Fix SimplexIterations getter and add BarrierIterations

[odow]

Closes #86

[codecov]

Codecov Report

Merging #87 (7b9c162) into master (94ae3b5) will increase coverage by 0.27%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #87      +/-   ##
==========================================
+ Coverage   82.29%   82.56%   +0.27%     
==========================================
  Files           3        3              
  Lines        1254     1262       +8     
==========================================
+ Hits         1032     1042      +10     
+ Misses        222      220       -2     

Impacted Files	Coverage Δ
src/MOI_wrapper.jl	93.35% <100.00%> (+0.24%)	⬆️

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