Added __str__ and __repr__ plus missing properties

[raff]

Implement #30 and add missing properties and methods
(real, imag, conjgate).

Also added tests.

[codecov-io]

Codecov Report

Merging #31 into master will increase coverage by 0.18%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #31      +/-   ##
==========================================
+ Coverage   64.86%   65.04%   +0.18%     
==========================================
  Files          55       55              
  Lines       10074    10091      +17     
==========================================
+ Hits         6534     6564      +30     
+ Misses       3079     3065      -14     
- Partials      461      462       +1

Impacted Files	Coverage Δ
py/complex.go	31.17% <100%> (+14.83%)	⬆️
py/property.go	14.28% <0%> (+14.28%)	⬆️

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[ncw]

That looks great - thank you :-)