Add integer rounding to match APE 14

[WilliamJamieson]

Fixes #524

[codecov]

Codecov Report

Attention: Patch coverage is 83.33333% with 1 line in your changes missing coverage. Please review.

Project coverage is 87.44%. Comparing base (9cd8552) to head (6cfcc53).
Report is 7 commits behind head on master.

Files with missing lines	Patch %	Lines
gwcs/api.py	83.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #525      +/-   ##
==========================================
+ Coverage   87.42%   87.44%   +0.01%     
==========================================
  Files          22       22              
  Lines        3874     3888      +14     
==========================================
+ Hits         3387     3400      +13     
- Misses        487      488       +1     

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