delete README symlink

Readers should just look at README.md, or the generated README.html.
run.sh: set Mac OSX DYLD_LIBRARY_PATH

DYLD_LIBRARY_PATH is the Mac OSX equivalent of Unix LD_LIBRARY_PATH.
main: suggest thrd_yield() for -y fairness
README.md: update much of the README

Integrate some info from the website and the OOPSLA artifact submission,
and improve the whole thing to be a single reference document.
README.md: add extra blank lines
README.md: push URLs down to See Also section
README.md: point non-git users to gitweb