and yet each time a different problem :) that why i stated that i already had a two similar posts ;) on the other hand bit-strings/bit-vectors (terms sometimes uses interchangeably, though i do not like that) are quite different. there is very little room to maneuver as the description of a string is what is being the focus of compression.
for future reference :
it seams http://bitmagic.io/ has some interesting solutions.