Version 0.4.0 (Pre M1)

• 108 PRs
• Unit Tests for Python 3.4
• Removing datastore.Dataset class and moving functionality elsewhere
• Removing Entity.delete(), Entity.save() and Key.get() methods
  in the datastore. Adding top-level put(), get() and delete() methods
  to replace
• Adding datastore Batch class for non-transactional saves/gets/deletes.
• Making Key, Entity, Transaction, Query, etc. available in
  datastore namespace
• Making Bucket.delete() fail if there are more than 256 objects and
  allowing silent 404s on object deletes (since list of objects in a
  bucket is eventually consistent)
• Made PyOpenSSL dependency optional (via oauth2client). It is required
  for creating signed URLs for Storage buckets and objects.
• Removing boto aliases in Storage
• Using Google Application Default Credentials
• Adding resumable upload support from apitools
• Enabling datastore.set_defaults() to simplify auth and default dataset ID
• Allowing inferred dataset ID, which can be re-used in constructors
  throughout (env. var, App Engine and Compute Engine supported)
• Renaming Key noun in storage to Blob
• Correctly handling indexing of list values in datastore
• Using value of more_results from datastore query responses
• Changing datastore Query to accept most properties in constructor
  and isolate other properties (e.g. limit, offset) to fetching
• Adding user friendly datastore allocate_ids top-level method
• Support eventual consistency (or not) in datastore Connection
• Remove Key.from_path, Blob.from_dict, Bucket.from_dict and other
  classmethod factories in favor of easier to use constructors
• Sync mtime with update time on Storage objects/blobs
• Adding convenience Query.keys_only() method