Cyptocat audits

See discussion in #1163 about dubious security in Cryptocat per recent audits. The first commit here adds a summary of the audit findings to the English. At the very latest I think this needs to be included (and urgently translated). However per discussion on the previous issue I would take it one step further and remove the recommendation entirely pending it receiving a clean(er) bill of health. As noted the second commit should be easily reversible if it was decided to re-add it in the future.