This is a small and simple helper utility which helps us to
solve the "wordle" puzzle (see http://nytimes.com/games/wordle/
for details).

Thanks for the https://github.com/dwyl/english-words.git
repository for English words database, I just used the words_alpha.txt
file from the repository.

With this helper you can specify "not in a word" letters (gray
in original game), in word but not in place letters (yellow
in the original game) and "in place" letters (green in the
original game). And then the utility prints the list of
words which match the specified pattern.

Note 1: The word length is flexible and may be specified
via command line switches. Of course the default is 5.
Use "-h" command line switch for more details.

Note 2: This is my first Rust experience, so I'm
open for constructive criticism.