Update flask-login to 0.4.0

[pyup-bot]

There's a new version of flask-login available.
You are currently using 0.3.2. I have updated it to 0.4.0

These links might come in handy: PyPI | Changelog | Repo | Docs

Changelog

0.4.0

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Released on October 26th, 2016

• Fixes OPTIONS exemption from login. 244
• Fixes use of MD5 by replacing with SHA512. 264
• BREAKING: The login_manager.token_handler function, get_auth_token method
  on the User class, and the utils.make_secure_token utility function have
  been removed to prevent users from creating insecure auth implementations.
  Use the Alternative Tokens example from the docs instead. 291

Got merge conflicts? Close this PR and delete the branch. I'll create a new PR for you.

Happy merging! 🤖