* Added non-standard `resource` compound view.
* Removed Python 3.3 support, added 3.7, removed deprecated testing dependency.
* Scheme objects hash as per their string representation. 5
* Dead code clean-up.
* Additional tests covering previously uncovered edge cases, such as assignment to a compound view property.
* Restrict assignment of rootless paths (no leading `/`) if an authority part is already present. 8
* Enable handling of the following schemes as per URL (colon + double slash):
* `sftp`
* `mysql`
* `redis`
* `mongodb`
* Correctly represent scheme- (protocol-) relative URI.