Release 4.3.0

• Update travis for 4.3 (Serge Latyntcev) - 3643275
• FIX Cancel move operation if block move data is not provided (Garion Herman) - 32798e0
• FIX Correct check for block being shifted to top of list (Garion Herman) - e8d5ecf
• Upgrde dependencies (Maxime Rainville) - 483dd76
• FIX Handle edgecase when Element is 'moved' to the same place (Garion Herman) - 893f2d0
• FIX Resolve issues with drag/drop behaviour on Elements (Garion Herman) - 21e66e5
• Make sure ignored_classes are ignored (GitHub) - 7eee13f
• DOCS Update Adding blocks between blocks image and content (Sacha Judd) - ebe5b96
• NEW Tweak child rendering error translation key, add to lang files (Garion Herman) - 019d806
• NEW Introduce error boundary to Element for softer crashes (Garion Herman) - 2c025c6
• NEW ability to configure content field replacement (Dylan Wagstaff) - [5d1df63](5d1df63
  17c42ee)
• Add configuration to allow not replacing the 'Content' field to enable backwards compatibility with older content blocks modules. (Dylan Wagstaff) - cd7dd78
• Bump mixin-deep from 1.3.1 to 1.3.2 (GitHub) - a2918f6
• BUG AddElementPopoverComponent target on HoverBar wasn't matching an actual target. (Maxime Rainville) - b996f05
• BUG Remove unused method from AddElementPopover (Maxime Rainville) - 1913ee5
• Answer PR feedback (Maxime Rainville) - ce72d57
• Doc type of cssPrefix argument (GitHub) - f9e2992
• Bring back element-editor top class wrapper (Maxime Rainville) - 0160e43
• API Add classname utility method to prefix class names (Maxime Rainville) - 90f1013
• FIX Make the HoverBar in-between block more visible (Maxime Rainville) - 953b6d9
• Fix 'User help guide' link in Introduction section (GitHub) - a6002d5