Correct --expand=product: generate product of words, not characters
Change -n to to more descriptive -r/--repeat
Read from stdin if no --dict_file or passphrase arguments are provided
# Add --expander charcteristics comment, based on itertools documentation
Merge branch 'master' into candidate-performance
Don't use ''.join() when --expand is used, ~10% speedup
- Filters and results generator now consume ('word1', word1', ...)
  instead of 'word1word2...'
gen_eckey: Check either `pkey` is provided or `passphrase` was provided, not both
Refactor --expander into seperate expand_wordlist.py, ~2x speedup on multicore