Update migrations.rst

missing quote marks around update on addForeignKey example
Merge pull request #326 from x20mar/patch-1

Update migrations.rst
Merge branch '0.3.x-dev'
starting to improve docs
improving docs
Make Util return timestamps in UTC, fixes 354
formatting
Merge pull request #355 from ushahidi/utc-migration-timestamp

Make Util return timestamps in UTC, fixes #354
Merge pull request #356 from robmorgan/master

Master