Update flask-dance to 2.0.0

[pyup-bot]

This PR updates flask-dance from 1.2.0 to 2.0.0.

Changelog

2.0.0

---------------------

Changed (**backwards incompatible**)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
* The backwards-compatible references to "backend" have been removed.
Use "storage" instead.
* The columns defined in ``OAuthConsumerMixin`` now set ``nullable=False``.
If you are using the SQLAlchemy storage and are upgrading from a previous
version of Flask-Dance, you may want to do a database migration.
* Previously, Flask-Dance had an undocumented
feature where it would automatically redirect based on a ``next``
parameter in the URL. This undocumented feature has been removed.
* All pre-set configurations now use a consistent
naming scheme for pulling client IDs and client secrets from the app config.
The following configurations have changed: Dropbox, Meetup, Twitter,
and Zoho.
* Replace ``lazy`` dependency with
`werkzeug.utils.cached_property <http://werkzeug.pocoo.org/docs/0.14/utils/werkzeug.utils.cached_property>`__

1.4.0

---------------------

Changed
~~~~~~~
* "Backends" are now called "Storages", since the word "backend" means
something different in the context of web development. This release
is fully backwards-compatible, but deprecation warnings have been
added anywhere that you import and use a backend (rather than a
storage).

Added
~~~~~
* Add ``oauth_before_login`` signal
* Add ``reprompt_select_account`` parameter to google blueprint

1.3.0

---------------------

Added
~~~~~
* Add ``authorization_required`` decorator
* Added Authentiq pre-set configuration

Links

• PyPI: https://pypi.org/project/flask-dance
• Changelog: https://pyup.io/changelogs/flask-dance/
• Repo: https://github.com/singingwolfboy/flask-dance

[codecov]

Codecov Report

Merging #176 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #176   +/-   ##
=======================================
  Coverage   74.11%   74.11%           
=======================================
  Files          10       10           
  Lines         309      309           
=======================================
  Hits          229      229           
  Misses         80       80

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