Switch Debug Flag from int to bool

[kaypee90]

resolves #50

[954-Ivory]

Please review this PR.

This PR is error.
When we set the DEBUG=0 in envs file, we will get a str type: '0'.

bool(os.environ.get("DEBUG", '0')) # This will be True

So, we need change it to:

bool(int(os.environ.get("DEBUG", default=0)))

#50 (comment)