[Feature Request] write to file/output to file.

[r0oth3x49]

1st of all i would like you thank you for this great project @PatrikHudak . I have one feature request and a minor change to make work on windows as well.

Feature Request

• you can add option to write to the file instead of using Mem.
  • running dnsgen against 5 to 6k subdomains eats up all the Memory and the process gets killed so in that case writing to file will be helpful and plus point is massdns also accepts file as input to resolve.
    • this feature will save people using this great project with less RAM

Change to make it platform independent

• you can use python's os module to get the path to words.txt the current one is nice but instead of hard coding the path as /words.txt we can use

os.path.join(pathlib.Path(__file__).parent, "words.txt")