Rust libray build:
```
cargo build
```


Python test:
```
python call_in_python.py
```


C test:
```
gcc call_in_c.c -L target/debug/ -lstringtools
```


NodeJS test:
```
npm install ffi
node call_in_node.js
```


Reference:
http://siciarz.net/24-days-of-rust-calling-rust-from-other-languages/