Expose library commands

[andrewdea]

Currently, the package is most useful as a CLI, but we cannot import most of its functionalities into python code.

I have created this PR to expose the most useful commands:

• code_complexity to compute the complexity of any snippet (string) of code
• file_complexity to compute the complexity of a file

[rohaquinlop]

@andrewdea would be great if we have this functions in the documentation, if you want you can add it, or I can do it if you want to.

[andrewdea]

@rohaquinlop great point! I'll go ahead and add docs today
tracking this here

[andrewdea]

@rohaquinlop I think we can close this thanks to the merge.

Once we have the docs done, we'll be ready for a new release? Just checking if there's any additional steps