Improve code sample by formatting the code, and including some code cleanups

[nnja]

Improved the sample code by making the following updated:

• Removed a user-specific file from the .vscode folder and added it to .gitignore
• PEP8ified and formatted the code, standardized use of double quote " throughout code files
• Formatted the templates
• Removed an errant print statement
• Formatted the imports, removed relative imports in favor of absolute imports
• Pulled out a variable in hello\urls.py to make the code cleaner
• Use __str__ instead of __unicode__ for representing models in Django using Python3. Fixed variables. Since the tutorial is targeted for python 3.6, changed the return value to an f string.

A PR to update the docs based on these changes is located here: microsoft/vscode-docs#1869

[nnja]

cc/ @kraigb for review