add nodes/edges softmax and readout

[CarloLucibello]

No description provided.

[codecov]

Codecov Report

Merging #48 (d4db332) into master (b2f6ebf) will increase coverage by 1.37%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #48      +/-   ##
==========================================
+ Coverage   78.24%   79.62%   +1.37%     
==========================================
  Files           8        8              
  Lines         662      697      +35     
==========================================
+ Hits          518      555      +37     
+ Misses        144      142       -2     

Impacted Files	Coverage Δ
src/utils.jl	81.72% <ø> (+14.41%)	⬆️
src/gnngraph.jl	80.57% <100.00%> (+0.17%)	⬆️
src/layers/pool.jl	100.00% <100.00%> (+5.26%)	⬆️

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