Fix #528 Youtube API amendments for testing
- Changed handle_response definition, does not take tuple anymore

- Switch from class to module

- Made appropriate changes in cli.py

- Divided up code fore more testability
Pin flake8, pep8, and pytest at known working versions
Fix #523 Create New Talk popup

- Add NewTalkWidget class which has its own instance of TalkDetailsWidget
- Add instance of NewTalkWidget to TalkEditorApp and display it as a modal
  dialog when Add New Talk button clicked
- Add apply_changes function to repopulate the presentationModel and select
  the last updated talk in the table view with select_row function
- Add new talk to database when Add button clicked, close dialog and call
  apply_changes
- Refactor update_talk to use apply_changes, and prevent title-less talks
- Refactor create_presentation to accept a TalkDetailsWidget instance
- Set dialog appearance (title, size, buttons, placeholder text, date format)
- Keep previously entered room, event, date and time in NewTalkWidget
- Remove unused functions from TalkEditorApp:
  confirm_add, clear_talk_details_widget
- Remove unused files that were components of the old Talk Editor:
  AddTalkWidget.py, EditorWidget.py, UnlockTalkWidget.py
Close #506 Add rss feed attribute tests
Add a test that pulls different rss feed attributes such as title, speaker, etc.
and compares it to a JSON file with the expected results

test_get_presentations(): pulls attributes title, speaker, level,
status, time, event and room and checks that they contain
correct values