Add hasbox to check for Core.Box

[timholy]

No description provided.

[codecov]

Codecov Report

Merging #29 (522e9db) into master (1916295) will decrease coverage by 0.13%.
The diff coverage is 88.88%.

@@            Coverage Diff             @@
##           master      #29      +/-   ##
==========================================
- Coverage   93.97%   93.84%   -0.14%     
==========================================
  Files           4        4              
  Lines         332      341       +9     
==========================================
+ Hits          312      320       +8     
- Misses         20       21       +1     

Impacted Files	Coverage Δ
src/MethodAnalysis.jl	93.75% <88.88%> (-0.80%)	⬇️

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