[RFC] Define a public API

[ripariancommit]

Situation

Whereas...

1. The project claims to conform to semantic versioning. And the semver spec 2.0 requires that you define a "public API" - changes to which should either rev the major or minor version number depending on if they are backwards compatible or not.

2. PEP 8 recommends that you use the __all__ module variable to define your public interface.

3. We do not clearly define a public API.

Proposal

1. Make use of the PEP 8 __all__ variable throughout the project to define our public interface.

2. In all submodules, add an __all__ variable that defines what classes and methods within that module are considered "public".

3. In the top-level rule34Py module, import all submodule elements declared in __all__; thereby creating a top-level public interface.

4. Update our project documentation to make our public interface clear.

5. Update our project policy to require a major version upgrade when changes are merged that break backwards compatibility in the public API, and a minor version change when merging changes that alter the public API in a backwards compatible way.