Fixed array with single or multiples entries on json extractor

[felipehertzer]

This pR fixes the issue found #140 where the @graph and liveBlogUpdate item can be an array with only one item or an array with multiple items.

Single Item with different structure:

"liveBlogUpdate": {
      "@type":"BlogPosting",
      "headline":"Coming this April, HBO NOW will be available exclusively in the U.S. on Apple TV and the App Store.",
      "datePublished":"2015-03-09T13:08:00-07:00",
      "articleBody": "It's $14.99 a month.<br> And for a limited time, …"
    }

Multiple items with array:

"liveBlogUpdate":[
    {
      "@type":"BlogPosting",
      "headline":"Coming this April, HBO NOW will be available exclusively in the U.S. on Apple TV and the App Store.",
      "datePublished":"2015-03-09T13:08:00-07:00",
      "articleBody": "It's $14.99 a month.<br> And for a limited time, …"
    },
    {
      "@type":"BlogPosting",
      "headline":"iPhone is growing at nearly twice the rate of the rest of the smartphone market.",
      "datePublished":"2015-03-09T13:13:00-07:00",
      "image":"http://images.apple.com/live/2015-mar-event/images/573cb_xlarge_2x.jpg"
    },
  ]

[codecov-commenter]

Codecov Report

Merging #143 (fbbd55a) into master (7224971) will not change coverage.
The diff coverage is 50.00%.

@@           Coverage Diff           @@
##           master     #143   +/-   ##
=======================================
  Coverage   94.95%   94.95%           
=======================================
  Files          19       19           
  Lines        2714     2714           
=======================================
  Hits         2577     2577           
  Misses        137      137           

Impacted Files	Coverage Δ
trafilatura/json_metadata.py	86.32% <50.00%> (ø)

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[adbar]

Hi @felipehertzer, thank you for the prompt answer! Could you please add test cases as well?

[adbar]

@felipehertzer Nevermind, I took the time.

Looks ready to merge.