Add comments to 'layout' setting

Comments are usefull here, because:
- it's not obvious how to adjust 'layout'
- sublime.Window.set_layout() isn't covered in sublime's official docs
  It is covered only in unofficial docs
  http://sublime-text-unofficial-documentation.readthedocs.org/en/sublime-text-2/reference/api.html
Fix spelling mistake in comments
Fix spelling mistake in comment
Merge pull request #73 from dnsmkl/master

Add comments to 'layout' setting (without typos)