Consider using classical recursion instead of manual recursion for the generator

[josecelano]

Relates to: #12

The JSON generator uses a manual recursion (with the help of the custom type Stack).

@da2ce7 made a proposal using classical recursion here.

We could try to refactor the generator and compare both implementations.

I have the feeling that classical recursion would increase readability, and I don't think that would have a big impact in performace. I used the Stack becuase:

• I decided to port the C implementaion first without making changes and refactor later after adding tests.
• My first attempt was not succesfull. In fact, I started from scratch with classical recursion but without separating tokenizer from generator (parser). It was a mess and I decided to go with the port from C and refactor later.

If we implement this, I think we would have a 100% classical approach: tokenizer + parser with recursion. I think that's good because I think it's a common pattern. On the other hand, I think it would be even easier to add generators for other formats.

We can also continue with the current version until we add other formats. I don't think the Stack version is very hard to follow.

cc @da2ce7 @magecnion