encodings.py: wrapper(): always return a string

Make the unwrapped case -- with a lambda -- produce a ''.join(x) rather
than just identity, for compatibility with the calling function
encodings.py: use OptionParser; implement -w

Wrapping behavior is no longer hard-coded
encodings.py: implement a crude --html option

Generate hard-coded HTML page for inclusion on GitHub
encodings.html: Generated output with --html
README.md: Include link to rawgit HTML page