Onion url human readable encoding schemes

This software encodes onion urls into human readable urls made up
of words.

- otp.py
This follows RFC2289 for OTP to trasform the 80 bit onion url
into 7 words and a number. It achieves this by splitting 80 bits
into 7 11 bit blocks + 1 3 bit block. On the 7 11 bit blocks we
map each bit block with a word from the 2^11 big word list and the
3 bit block to a maps of numbers from 1 to 8.

example:
- To mnemonic url -
./onionconv.py -o jv6g2ucbhrjcnwgi
mnemonic url: anti-stan-bawd-fled-noll-fee-cant-1.onion

- ... and back -
./onionconv.py -m anti-stan-bawd-fled-noll-fee-cant-1.onion
onion url: jv6g2ucbhrjcnwgi.onion

TODO:
- pet.py
Still to be implemented, but the main idea is to get a 2^11 long list of
the first three letters of common english words. One can then generate a
url that is made up of any word that starts with these three letters.
example:
THIs-CAN-BECome-THE-URL-FOR-THIs-SITe.onion

in this case the search is only made on the characters THI,CAN,BEC,THE,URL,FOR,THI,SIT.

Maybe it could be a good idea to create special cases for 2 and 1 letter words.