FIX: Ensure short pipes with valves are reduced to just valves

[tasseff]

@jjstickel, assuming this corrects the issue we were discussing, this should close #112. It doesn't ensure that all short pipes don't have adjacent valves, but it does ensure that when parsing EPANET files, we will not decompose a short-enough pipe with a valve into a short pipe and a valve.

If we want to pursue a more careful reduction of the network (e.g., ensure short pipes and valves never exist in sequence), I think this would be more easily facilitated by using a package that inspects the graph structure of the network (e.g., LightGraphs.jl).

[codecov]

Codecov Report

Merging #113 into master will increase coverage by 0.30%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #113      +/-   ##
==========================================
+ Coverage   80.55%   80.85%   +0.30%     
==========================================
  Files          27       27              
  Lines        2206     2210       +4     
==========================================
+ Hits         1777     1787      +10     
+ Misses        429      423       -6     

Impacted Files	Coverage Δ
src/io/epanet.jl	72.32% <100.00%> (+1.32%)	⬆️

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