Command to move line up or down in Atom Editor
In Atom you can just use Ctrl + Up.
You can find these options on Atom menu : Edit > Lines > Move Line Up
Windows: Ctrl+Up/Down
Mac: Ctrl+Cmd+Up/Down
Don't have enough Rep to leave as a comment. But for @DanielM question.
To move several lines in Atom:
Select all the several lines you want move by mouse or by holding shift and moving up or down the lines you want, and then use either the commands for Windows Ctrl+Up/Down or Mac Ctrl+Cmd+Up/Down
Note: The whole line does not have to be selected as long as part of it is, it will move with the commands.