Add 'full-file' support, getopt, verbose.

[mino98]

Adding minimal getopt support:

$ ./passpwn -h
Usage: ./passpwn [-h] [-v] [-f]

If you enable "full-file mode" (-f) then every line of the file is checked against passpwn, rather than just the first line. This is obviously much slower but potentially helpful for messy people like myself, if you have credentials in line other than the first of each file.

Verbose (-v) prints the current file and string, for debugging.

Works on MacOS and should work on Linux, but I haven't tried it and OSX getopt is different from linux's.