v0.2.0

This release includes:

• A pytest integration and some first basic tests
• A new, decentralized processor registration system. Each submodule now has a register function (e.g. register_divisions in divisions.py) that registers the corresponding processors. These functions can also be imported when building a custom extension using this package. Note that individual processors should be imported from their submodules (e.g. from leidenmark.divisions import DivisionsPreproc instead of the former from leidenmark import DivisionsPreproc).