Make Popen args a sequence

[de1iza]

Closes #8

The args passed to Popen should be a sequence not a string.

From subprocess.Popen documentation:

args should be a sequence of program arguments or else a single string or path-like object. By default, the program to execute is the first item in args if args is a sequence. If args is a string, the interpretation is platform-dependent and described below. See the shell and executable arguments for additional differences from the default behavior. Unless otherwise stated, it is recommended to pass args as a sequence.
On POSIX, if args is a string, the string is interpreted as the name or path of the program to execute.

[de1iza]

By the way, thank you for your work, @anijackich, it helped me a lot!