Fix install script phase to not fail.
Fix install script phase to not fail.

* Use -R to copy symlinks instead of trying to follow them. Otherwise copying
  the Sparkle framework infinitely recurses.
* rm the existing application before copying into place.

Fixes #31

ianyh/Amethyst,ianyh/Amethyst,olsonpm/Amethyst,ianyh/Amethyst,hooplaaa/Amethyst,m4rw3r/Amethyst,egabancho/Amethyst,egabancho/Amethyst,olsonpm/Amethyst,cevaris/Amethyst,ianyh/Amethyst,cevaris/Amethyst,m4rw3r/Amethyst,hooplaaa/Amethyst,ianyh/Amethyst