How can I split a movie into sections?
I haven't used it personally, but it looks like Subler will do what you want. 

Here is the proper format you need to use for the chapter file: https://code.google.com/p/subler/wiki/ChapterTextFormat


  Subler will allow you to add chapters. You just need to drag and drop a
  text file in the right format into Subler. You don't write them in in
  the Subler GUI.
  
  The Subler site explains the format. It took a lot of trial and error
  for me to get it right and it is time consuming so I haven't done it
  in a while. Otherwise, I'd tell you how I did it.
  
  Once you add the file, you will have a new row under the Video Track
  and Stereo rows called Chapter Track. You can edit the Titles in there
  if you want to, but if you created the file correctly, you shouldn't
  have to.


http://forums.macrumors.com/showthread.php?t=901354