1.2:
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 * Fix and improve markup_element check for consistency

1.1:
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 * Secure some external target _blank links by living standard rel="noopener"

1.0:
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 * Silence possible eventData property check and (clean) Up to 2.0
 * Raises requirements

0.9:
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Changed static call to proper $this

0.7:
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Changed ClickableURL to prefix http:// for www. only links

0.6:
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Added 'Twitter' markup