Update README.md due to 8dff45d (#375)

README.md

@@ -102,8 +102,8 @@ pprof can read `perf.data` files generated by the
 
 ## Further documentation
 
-See [doc/pprof.md](doc/pprof.md) for more detailed end-user documentation.
+See [doc/README.md](doc/README.md) for more detailed end-user documentation.
 
-See [doc/developer/pprof.dev.md](doc/developer/pprof.dev.md) for developer documentation.
+See [CONTRIBUTING.md](CONTRIBUTING.md) for contribution documentation.
 
-See [doc/developer/profile.proto.md](doc/developer/profile.proto.md) for a description of the profile.proto format.
+See [proto/README.md](proto/README.md) for a description of the profile.proto format.