Fix PHP Notice and remove extract() function

Remove `extract()` function for shortcode attributes as is recommended for plugins and themes and has been adopted by WordPress core (see https://core.trac.wordpress.org/ticket/22400).
Fix PHP Notice: Undefined variables title and data on line 139
Remove muted attribute for `fa` shortcode: it is not used already and it is not a valid class for fontawsome
Merge pull request #4 from CybMeta/patch-1

Fix PHP Notice and remove extract() function