Implement show

[blegat]

cc @tweisser

[codecov-io]

Codecov Report

Merging #11 into master will increase coverage by 3.72%.
The diff coverage is 86.2%.

@@            Coverage Diff             @@
##           master      #11      +/-   ##
==========================================
+ Coverage   88.01%   91.73%   +3.72%     
==========================================
  Files           9        9              
  Lines         367      387      +20     
==========================================
+ Hits          323      355      +32     
+ Misses         44       32      -12

Impacted Files	Coverage Δ
src/variety.jl	90.16% <100%> (+17.28%)	⬆️
src/basic.jl	86.2% <100%> (+9.73%)	⬆️
src/SemialgebraicSets.jl	61.53% <25%> (+16.08%)	⬆️
src/fix.jl	92.98% <75%> (+2.41%)	⬆️

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[coveralls]

Coverage increased (+4.0%) to 92.157% when pulling af3fda5 on bl/show into 25909e4 on master.