* Documentation:
* Migrated to `pydata` theme.
* Updated installation steps.
* Package:
* Exposed `DEFAULT_CACHE_STORAGE_BASE_DIR`, `make_cache_dir`.
* Updated `AUTHORS.md` and `HISTORY.md`.
* `DblpConnector`:
* Improved `DocType` handling.
* Implemented timer to mitigate rate limitation queries.
* Fixed URL when data is fetched through the XML API.
* Bug fix:
* Fixed `DocType.__str__`.
* Fixed `Query.__str__`.
* Improved tests to be more robust to network failures:
* `GoogleScholarConnector`.
* `HalConnector`.