update Flask example

[bevennyamande]

• Declare variables inside an application context, i encountered an issue when i was testing an application whilst i was logged into facebook
• Adding changes to flask.ext.sqlalchemy accordingly
• Updated current version of facebook API

[martey]

Thank you for this contribution. This looks good, but I would appreciate it if you could use black to ensure that your changes are linted correctly (see https://app.circleci.com/pipelines/github/mobolic/facebook-sdk/45/workflows/6d6de8b8-dd50-46ef-a938-fda63f05ec37/jobs/871/parallel-runs/0/steps/0-103?invite=true).

[bevennyamande]

Ok thanks for the review let me check using black , but i think this repo needs updates accordingly as the Facebook Graph API is also changing

[bevennyamande]

I dont know where and how my build are failing will have a look at the deeper code

[martey]

Please see the [contributing guidelines:

A pull request should only include commits directly applicable to its change (e.g. a pull request that adds a new feature should not include PEP8 changes in an unrelated area of the code).

As per the link in my previous comment, you only needed to lint examples/flask/app/views.py. If you want to add support for new versions of the Graph API, or change how the library determines what default version to use, you should create a new pull request.