René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Update Key API to be more user-friendly per design doc discussion","articleBody":"Related ~~to #3 and~~\nhttps://docs.google.com/document/d/1xKw8Tz6lfN5uOcv0my4uUgFSeDoRzwCLho2UGlBpqDU/edit\n\nPlan to make this work:\n- [x] Remove `Key.from_path` (since will be new constructor) (#456)\n- [x] Remove all setters (#458)\n- [x] Make `parent` re-use an instance (since immutable) (#459)\n- [x] Make `Key` constructor act like `Key.from_path` (#460)\n- [x] Make `Key.complete_key` method (needs better name) to act like `Key.id(new_id)` (#461)\n- [x] Implement `Key.compare_to_proto` to check a key against a retrieved key (needs better name) (#462)\n- [x] Require `dataset_id` on `Key` (may require removing `dataset_id` from `Key protos) (#463)\n- [x] Add `parent` to constructor (#476)\n- [x] ~~Update docstrings and other docs to reflect changes (including `__repr__`, probably shouldn't have `path`)~~ (Putting off bulk doc fixes until API is stable again)\n- [x] ~~Change `Entity` constructor to only accept a `key`. (This can probably move to a new bug, which I have yet to file.)~~ (filed #484)\n","author":{"url":"https://github.com/dhermes","@type":"Person","name":"dhermes"},"datePublished":"2014-12-19T20:21:08.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/451/google-cloud-python/issues/451"}