O365

Features:
- Connection: When using the credentials auth_flow_type the tenant_id is now required
- Message: added 'unique_body' property
- Calendar: added 'get_schedule' (get_availability)

Features:
- Message: You can now save Messages and attached messages as EML files.

Features:
- The library now features two different authentication flows:
- 'authorization': Authenticate on behalf of a user
- 'credentials': Authenticate with your own identity (the app)
- Drive: Added Drive.get_item_by_path(item_path)
- Drive: Now get_drives accepts limit, batch order_by and query parameters
- Mailbox: Now get_message allows to specify an object_id and expands or selects as well
- Account: scopes param on account.authenticate are now optional
- Sharepoint: some enhancements

Features:
- Bug fixing release

Features:
- It is now posible to authenticate from a web environment with the changes on Connection.
- Attachment: Added attribute size to attachments
- Attachment: You can now add in memory files to attachments. Pass a tuple (BytesIO instance, 'file name.png')
- Account: the resource ME_RESOURCE is now the default
- Message: Added new method 'mark_as_unread' to mark the message as unread.
- Message: Added Body Preview
- Query: Added Precedence Grouping
- Query: Now it's possible to pass attribute=None to the iterable method so you can iterate on the object itself. See [271](https://github.com/O365/python-o365/issues/271)
- Connection: If timezone is unkknown default to UTC
- Connection: self.naive_session is now lazy loaded
- OutlookWellKnowFolderNames: Added ARCHIVE

Features:
- Optimized library startup time by moving imports into methods