If you're running Windows 8.1 then I believe the only way to disable the Auto Snap feature is with a 3rd party program, I cant exactly test it myself as I'm on Windows 10. However; if you're running Windows 10 all you have to do is go into all
settings > system > multitasking, you can then turn off all snap options or just specific ones for your preference
Edit: For Windows 8.1, go into
control panel > ease of access center > make the mouse easier to use, then find and check the box labeled
Prevent windows from being automatically arranged when moved to the edge of the screen