docs: fix link to README in QuickStartGuide
# AFL quick start guide
-You should read [README.md](README.md) - it's pretty short. If you really can't, here's
+You should read [README.md](../README.md) - it's pretty short. If you really can't, here's
how to hit the ground running:
1) Compile AFL with 'make'. If build fails, see [INSTALL.md](INSTALL.md) for tips.
