pylint client, add docs
Add Challenge docs, pep8/docs interactive_challenge
More docs in challenge
Merge remote-tracking branch 'github/letsencrypt/master' into pep8

Conflicts:
	letsencrypt/client/client.py
Merge remote-tracking branch 'github/letsencrypt/master' into pep8

Conflicts:
	letsencrypt/client/client.py
Fix redirect var flow
ca_server -> server
Move redirect to authenticate
Fixed undefined variable from Kuba-PEP8
git push origin masterMerge branch 'kuba-pep8'