Fix CircleCI Tests and Other Improvements

[chriddyp]

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[chriddyp]

• 🔒 Removes the /static/ folder and endpoint that is implicitly initialized by flask. This is too implicit for my comfort level: I worry that users will not be aware that their files in their static folder are accessible
• ⚡️ Removes all API calls to the Plotly API (https://api.plot.ly/), the authentication endpoints and decorators, and the associated filename, sharing and app_url arguments. This was never documented or officially supported and authentication has been moved to the dash-auth package
• 🔧 Add two new config variables: routes_pathname_prefix and requests_pathname_prefix to provide more flexibility for API routing when Dash apps are run behind proxy servers. routes_pathname_prefix is a prefix applied to the backend routes and requests_pathname_prefix prefixed in requests made by Dash's front-end. dash-renderer==0.8.0rc3 uses these endpoints.
• ✏️ Fix a typo in an exception
• 📝 Update README.md
• ✅ Fix CircleCI tests. Note that the the dash-renderer contains the bulk of the integration tests. Fixes Update circleci #20
• 💄 Flake8 fixes and tests (fixes Flake8: Four F821 undefined name issues #99 )
• ✨ Added a CHANGELOG.md