Merge duplicate test.sh into one same as `Your First Graph` on README.md

Currently two version of test.sh reside on root directory and `script/`.
the one on root directory does not even works because it do not have proper setup for creating test service, label, etc.

Also I think it would be better to provide `Your First Graph` as script so user who build from source can test if server works correctly.

As far as I remember the intent of `test.sh` was same with `Your First Graph` so I am suggesting cleanup multiple `test.sh` into one same as `Your First Graph`