Fix Ogata simulation and add tests

[codecov[bot]]

Codecov Report

Merging #30 (f364bb3) into master (ab6f16e) will increase coverage by 8.79%. The diff coverage is 60.00%.

:exclamation: Current head f364bb3 differs from pull request most recent head 7c3d84c. Consider uploading reports for the commit 7c3d84c to get more accurate results

@@            Coverage Diff             @@
##           master      #30      +/-   ##
==========================================
+ Coverage   22.75%   31.54%   +8.79%     
==========================================
  Files          16       16              
  Lines         334      336       +2     
==========================================
+ Hits           76      106      +30     
+ Misses        258      230      -28     

Impacted Files	Coverage Δ
src/history.jl	74.46% <50.00%> (ø)
src/poisson/multivariate/suffstats.jl	35.00% <50.00%> (ø)
src/simulation.jl	75.00% <66.66%> (+75.00%)	:arrow_up:
src/poisson/simulation.jl	75.00% <0.00%> (-25.00%)	:arrow_down:
...isson/multivariate/multivariate_poisson_process.jl	55.55% <0.00%> (+11.11%)	:arrow_up:
src/abstract_point_process.jl	33.33% <0.00%> (+33.33%)	:arrow_up:
src/poisson/abstract_poisson_process.jl	68.75% <0.00%> (+68.75%)	:arrow_up:

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