Combinatorics: Print graphs nicely

[lkastner]

julia> G = complete_graph(5)
Graph{Undirected} with the following edges:
(2, 1)(3, 1)(3, 2)(4, 1)(4, 2)(4, 3)(5, 1)(5, 2)(5, 3)(5, 4)

julia> [G,G]
2-element Vector{Graph{Undirected}}:
 Graph{Undirected} with 5 nodes and 10 edges
 Graph{Undirected} with 5 nodes and 10 edges

[fingolfin]

Nice improvement. One question

[codecov]

Codecov Report

Merging #2786 (00b2ef2) into master (5756189) will increase coverage by 0.01%.
Report is 2 commits behind head on master.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master    #2786      +/-   ##
==========================================
+ Coverage   73.56%   73.58%   +0.01%     
==========================================
  Files         455      455              
  Lines       64419    64445      +26     
==========================================
+ Hits        47387    47419      +32     
+ Misses      17032    17026       -6     

Files Changed	Coverage
src/Combinatorics/Graphs/functions.jl	0.00%
...edralGeometry/Polyhedron/standard_constructions.jl	ø