Try to serialize requests to update the blog feed

Make a best effort to only allow one client/request to make the backend
HTTP request to the blog feed.

Addresses issue 928 (http://openhatch.org/bugs/issue928)
Use protocol relative link for training missions

This change means that on HTTPS pages, we will use a HTTPS IFRAME URL
for the Oppia instance.

Refs #1348
Merge pull request #1405 from paulproteus/end-mixed-content

Use protocol relative link for training missions
Adds doc on issue tracking and fixes small indent error
Merge pull request #1406 from willingc/doc-issue-tracker

Adds doc on issue tracking and fixes small indent error #1404
Remove un-used column distinct_months from Citations model

Includes south migration.
Remove an un-used citations test fixture.
Merge pull request #1407 from onceuponatimeforever/remove_column

Remove un-used column distinct_months from Citations model
Fix for bug https://github.com/openhatch/oh-mainline/issues/1401
Fix for bug https://github.com/openhatch/oh-mainline/issues/1401
Merge pull request #1 from onceuponatimeforever/Add_email_settings

Fix for bug https://github.com/openhatch/oh-mainline/issues/1401 (@onceuponatimeforever added email testing settings)
Merge pull request #1409 from Winterflower/master

Fix for bug https://github.com/openhatch/oh-mainline/issues/1401
Fix argv parsing

Before this patch, we were using $1 both for MAX_TRACKERS and BASE_DIR, which
was insane.
Check the YAML validity of the tracker list we downloaded

This way, if we get a CloudFlare timeout instead of a legit HTTP timeout, we can
still detect something weird happened, and retry.
Add Elana Hashman to Login Team
Use load(), as safe_load() can't handle python/unicode

Note that this is tragic and we should fix the underlying problem which is that
we generate weird python/unicode YAML structures.
Merge pull request #1410 from paulproteus/detect-more-bugimporters-api-errors

Detect more bugimporters api errors
Simplify the deploy script

Back in the day, the deploy script would also do a git push. This removes that
from the deploy script, and assumes that whatever is on the main git repository
as master is what you want to deploy.

This also means we can simplify the docs around the deploy script, because after
this change, it no longer depends on the local git configuration.
Merge pull request #1411 from paulproteus/elana-login-team

Add Elana Hashman to Login Team
Merge pull request #1412 from paulproteus/simpler-deploy-script

Simplify the deploy script
Store production-usable SMTP config in deployment_settings

Since d5e1cc9f3664de6019c11461b92245b8c0eb0e69 , we have a debugging-oriented SMTP
server explained in settings.py. If we deploy this commit, we will use the same
setting in production, which is not consistent with how email sending works on
linode.openhatch.org.

This setting therefore makes that explicit, thereby fixing outbound email
in production again.