message: Update README.md
  Quick fix of the minimum Qt version for lumina-core
diff: @@ -17,7 +17,7 @@ Other Files that get installed if "core" is built directly:
  ### Library Dependencies
  -1. Qt 5.2+ (specific modules listed below)
  +1. Qt 5.4+ (specific modules listed below)
  * concurrent
  * core
  * gui
  