These work for me (Sublime Text 2 v2.0.1 on OS X 10.7.5)
- ⌘-↑: start of buffer
- ⌘-↓: end of buffer
The CMD-up and -down combos are the default shortcut for moving to the start and end of text buffers on OS X. They work in Safari text areas, too, for example. As such, they are not listed in the keymap file.