Clarify the interface to kaiba.

[thomasborgen]

Right now the interface to kaiba is in process.py. The functions are called process and process_raises.

In the future we only want to bump major versions if we break anything that these interface functions returns or if we change their function signature(parameters).

I propose to move most of our code into private modules and in kaiba/__init__.py we will expose only the two functions.

What do you think @ChameleonTartu ?

[ChameleonTartu]

@thomasborgen I think it is a good idea and it will be simpler for both contributors and clients of the library.