* *: update ci and format (#248)

(cherry picked from commit dd413e47)

* *: improve build process and update rocksdb (#243)

Some trivial changes are applied:
- Refactor Makefile
- Refactor README.md
- Add the rust-toolchain
- Update RocksDB submodule
- Reorganize the tests structure

(cherry picked from commit 064ab221)

* make format

* allow nightly version fail

* minor fix