Make sure Python is backgrounded

Make sure Python is backgrounded so that the .app container doesn't stay open while Python is processing and so the open .app container doesn't stop multiple invocations of the app from being halted by macOS.

change

```& this_URL & "' 2>&1")```

to 

```& this_URL & "' > /dev/null 2>&1 &")```

in `main.scpt`