housekeeping
remove tox_avatar_hash
Update documentation after API changes

Commit ba6ae15a739257200b04a10b6ecd22fe210951e1 introduced some API
changes, update the documentation to reflect them.
Merge branch 'dubslow-housekeeping-docs' of https://github.com/ittner/toxcore
Merge branch 'master' of https://github.com/dubslow/toxcore
Tox object doesn't need to be passed to tox_hash.