atom-sticky-cursor package
Sticks cursor to the beginning/end of line if it was in the beginning/end of line when moving up/down/left/right (see gif below).
Add this to your keybindings:
'body':
'down': 'sticky-cursor:move-down'
'up': 'sticky-cursor:move-up'
'left': 'sticky-cursor:move-left'
'right': 'sticky-cursor:move-right'
If You are using autocomplete-plus, You'll have to rebind it's movement commands.