Updated the way splitting is done:
* split{below,right} make splits default to be created below or right.
  One might think this is already the default since it appears that
  the new window is made to the right/below, but focus is kept on the
  old one. However this is actually the new one.
* Removed custom remapping for splitting and switching pane. Since it
  now switches to below/right like I wanted, there's no need for a
  custom bind. Should probably try to use defaults anyway.
* Updated SplitRelSrc() to reflect the change of splitright.
Reordered functions to make more sense.
Better description for SingleCompile install checking.