Print longer arrays without newlines

[IanButterworth]

Saving JSON files with long arrays results in very long documents currently because of all the newlines.
This only prints newlines after array elements if the length of the array is > 5.

i.e.

{
  "x": [1,2,3,4,5,6,7,8,9,10]
}

instead of

{
  "x": [
    1,
    2,
    3,
    4,
    5,
    6,
    7,
    8,
    9,
    10
 ]
}

Fixes #291

[IanButterworth]

The travis error is just a Pkg download glitch

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.74%. Comparing base (55f8500) to head (191b727).
Report is 32 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #305      +/-   ##
==========================================
+ Coverage   92.60%   92.74%   +0.13%     
==========================================
  Files           6        6              
  Lines         311      317       +6     
==========================================
+ Hits          288      294       +6     
  Misses         23       23              

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[IanButterworth]

This shouldn't be merged as-is. Needs rethinking.
Also JSON3.jl doesn't print newlines for arrays, so I'm giving that a go for now

[gasagna]

Any chance this can be revived?

[quinnj]

Closing as stale and could use a more modern approach to how to configure