Quote properties on edges too

[gabriel-fallen]

When serializing in the DOT format MetaGraph (savedot function) was putting quotes around (non-XML) property values for vertices but not for edges of a graph. That broke my code when I tried to put labels containing several words on edges of my graph. So I went on and made serialization quote everything save for XML/HTML value in closer accordance with DOT language spec.

[gabriel-fallen]

@matbesancon @simonschoelly hi guys! I'm sorry to bother you but could anybody please look at my PR? 😅

[filchristou]

( I must say I do not have any rights/permissions to to accept this PR or whatever, but I am happy to help )

[codecov]

Codecov Report

Merging #40 (d9b89d5) into master (01d4dac) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master      #40   +/-   ##
=======================================
  Coverage   98.69%   98.69%           
=======================================
  Files           5        5           
  Lines         382      384    +2     
=======================================
+ Hits          377      379    +2     
  Misses          5        5           

Files Changed	Coverage Δ
src/persistence.jl	95.65% <100.00%> (+0.19%)	⬆️

[gabriel-fallen]

@gdalle thanks for merging, but above all thanks for your work on this library! 😃

[gdalle]

You're welcome! Could you maybe try this v0.8.0 with your own code, and see if you can spot any other issues you'd like to address? Since it's a breaking release, if there's more low-hanging fruit I want it

[gabriel-fallen]

@gdalle unfortunately, I don't work on that codebase currently (but I might get back to it next year). Anyway, it was only a very simple supplementary visualization to double-check the connectivity of the system, and the quoted labels were all we needed at that point. I don't remember even really using HTML there. Though, maybe I stuck <strong></strong> somewhere for clarity...

[gdalle]

Alright then. I'll leave it dormant for some time and if no other issue pops up this month I'll release