announce version 0.8.2 on website
Merge tag '0.8.2'

tag release 0.8.2
PEP8
release tags should start with "v"

I don't like it but the whole scientific python ecosystem (numpy*) seem to use this convention
hopefully push the commits to master instead of only to the tag

I thought it was nice to not "pollute" master with the release announcements but having (the commit) the tags (refer to) not available in the history of master makes git describe fail
use sets instead of list for used variables in matching

"id" and variables in the orderyby expr could potentially appear twice in the list
added FIXMEs
arg with default value
remove loop_wh_progress title argument

it was not used
added nonzero and cumsum to authorized attribute list
remove duplicate functions