Added deprecation message and removed a debug print statement

1) Added interpreter #!/usr/bin/python3 to allow for running as ./PVEDiscordDark.py
2) Remove redundant import of os after sys
3) Cleaned up carriage return characters ^M from file to resolve the following error: -bash: ./PVEDiscordDark.py: /usr/bin/python3^M: bad interpreter: No such file or directory

Fixes #26