Make OCaml the best scripting langauges

[bobzhang]

• Bindings to NodeJS core libraries and Built in functions (JS built in functions are slow, but it is fine in such scenario)
• Treating files ending with mlx in a special way, so that we compile it on the fly given the compiler is fast enough, (caching js files if is already built)

[bobzhang]

it's already there, time to create bindings for NodeJS!
https://github.com/bloomberg/bucklescript-addons

[bobzhang]

we can add an option as below:

bsc --bs-main main.ml

after all compilation, bsc will load nodejs to run main.js

User can also explicitly pass all files:

bsc --bs-main main.ml --bs-files *.ml *.mli

[bobzhang]

note it can also be used as a webpack loader #561

[bobzhang]

now it's real see #594