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 :-)