[bug 1078326] Breadcrumbs fix.
Revert "[bug 1078326] Remove the M2M tables."

This reverts commit e986ceb6ff36a6175e0a6412d7c579f6fcdbbf22.
[bug 1078326] Break out 0008 migration into own commit Part 1.
[bug 1078326] Break out 0008 migration into own commit Part 2.
[bug 1078326] Remove the M2M tables.

This reverts commit 410a5052bf4d9e5e48a567eb8fbca8e8acd56829.
[Bug 1074861] Add --no-use-wheel to docs and Travis.

This is a partial cherry-pick of
a1b32036209781c555285675e4d53e76408400e3. The difference is that it
doesn't change deployments.
Make CORSMixin support preflighted requests.
Add CORS to questions and answers APIs.