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
Merge pull request #1411 from paulproteus/elana-login-team

Add Elana Hashman to Login Team