* add composite access method `.retrieve_files()` that, for a given tool version, retrieves the contents of all files associated with a given descriptor type and writes them to a specified output directory, each at their relative location as indicated by the `ToolFile.path` property
0.2.0
* add access methods for the following endpoints: * `.get_descriptor()`: `GET /tools/{id}/versions/{version_id}/{type}/descriptor` * `.get_descriptor_by_path()`: `GET /tools/{id}/versions/{version_id}/{type}/descriptor/{relative_path}` * `.get_files()`: `GET /tools/{id}/versions/{version_id}/{type}/files` * endpoint access methods support passing [TRS URIs](https://ga4gh.github.io/tool-registry-service-schemas/DataModel/#trs_uris) * known issues: * relative_path values containing slashes not yet supported for `.get_descriptor_by_path()`