Change OS X framework to use `@rpath`.

Signed-off-by: Aron Cedercrantz <aron@cedercrantz.se>
Add default LD_RUNPATH_SEARCH_PATHS for OS X apps.

- This will set the `@rpath` used by the linker to include frameworks from the
"Frameworks" directory in the application bundle.

Signed-off-by: Aron Cedercrantz <aron@cedercrantz.se>
Update INSTALL_PATH comment to reflect rpath changes.

Signed-off-by: Aron Cedercrantz <aron@cedercrantz.se>
Merge pull request #3 from rastersize/rpath

Use rpath for OS X frameworks and applications