Change to s3boto monkeypatch to allow no auth

Change to s3boto monkeypatch to allow no auth - course images and
instructor photos shouldn't have auth strings

Fixed typo for attachment
Merge pull request #2316 from dglance/dglance-s3boto-url

Change to s3boto monkeypatch to allow no auth
Documentation fixes on s3boto monkeypatch
Merge branch 'master' of http://github.com/Stanford-Online/class2go into dca_new_working2
Merge pull request #2318 from Stanford-Online/jrbl-monkeypatch-docfixes

Documentation fixes on s3boto monkeypatch
Merge branch 'master' of http://github.com/Stanford-Online/class2go into dca_new_working2
closes #2332.  raises event when repopulating textbox
Merge pull request #2333 from Stanford-Online/jbau-graded-exam-repop-event

closes #2332.  raises event when repopulating textbox
initial commit for adding members
sending email
inviting single email addresses done
adding users via CSV -> celery task
include username in existing user invite email
added preenroll_only functionality
added python engineer job post with disabled link
fixed some english whoopsies
change python job description a bit (#2341)
class member promote/demote
NO-OP change to retry travis (tests pass locally)
regrader print record id's (#2344)

useful for forensics later