Mwdblib

Bugfix:
- `Malwarecage.search_*` methods were not working properly (regression at 3.2.0 release)

New features:
- Added `listen_for_objects` methods for continuous listening for recent object, can be useful for scripts using MWDB as feed.
- Added `retry_on_downtime` option to `MalwarecageAPI`
- Passing all kwargs provided to `Malwarecage` constructor to `MalwarecageAPI` object (no need to create it separately)

Improvements and bugfixes:
- `BadResponseError` when response from server doesn't look like correct JSON ("Probably MalwarecageAPI.api_url points to the Malwarecage web app instead of Malwarecage REST API.")
- Notification about missing CLI dependencies, when `[cli]` extras are not installed
- Fixed handling of 'parent' option in `mwdb upload blob` command

* [CLI] `mwdb fetch` gets destination path as a second argument, not as `--output` option because of a naming conflicts with formatter output modifiers.
* [CLI] Fixed `mwdb fetch --keep-name` behavior when original name is invalid or empty.
* Fixed `setup.py` which didn't work without pre-installation of dependencies.
* Added helper function `config_dhash` which allows to pre-evaluate dhash for MalwarecageConfig object contents.

Breaking changes:
* HTTPError exceptions are mapped to [MalwarecageError hierarchy](https://mwdblib.readthedocs.io/en/latest/mwdbexc.html)
* Removed deprecated `MalwarecageFile.download_content`, use `download()` method instead

New features:
* Command-line interface (extra package `mwdblib[cli]`)
* mwdblib is reporting its version via User-Agent
* `Malwarecage.query()` should properly handle other hashes than SHA-256
* Various bugfixes and improvements

- Delaying requests when rate limit has been exceeded
- `recent_*` should be more effective (using `older_than=` query instead of deprecated `page=`)
- `verify_ssl` is set to True by default
- Slightly improved error handling

* Trailing slash is automatically added to api_url