Drugbank-downloader

What's Changed
* Add a better error for unapproved by cthoyt in https://github.com/cthoyt/drugbank-downloader/pull/3
* Update packaging by cthoyt in https://github.com/cthoyt/drugbank-downloader/pull/4
* speed up parsing with `lxml`

**Full Changelog**: https://github.com/cthoyt/drugbank-downloader/compare/v0.1.1...v0.2.0

- Fixed 1

Change API for `parse_drugbank()` to return the element tree and introduce `get_drugbank_root()` to automatically get the root.

Add automatic configuration of DrugBank credentials