README.md: add known issues section warning about nasty symlinks bug in listen
README.md: add known issues section warning about nasty symlinks bug in listen

100star/guard,baberthal/guard,yujinakayama/guard,garettarrowood/guard,pjump/guard,guard/guard,ginkel/guard,sdgdsffdsfff/guard,sideci-sample/sideci-sample-guard