Migrations shouldn't fail RuboCop checks - especially lint checks, such
as the nested method check. To avoid changing code in existing
migrations, add the magic comment to the top of each of them to skip
that file.
Upon tagging a repository, an error due to a missing migration occurred:
```
PG::Error: ERROR: column "taggings_count" does not exist
LINE 1: UPDATE "tags" SET "taggings_count" = COALESCE("taggings_coun...
```
Ran `rake acts_as_taggable_on_engine:install:migrations`, removed the first
migration that created the `tags` and `taggings` table, and added the rest.
Closes#1512
Closes https://github.com/gitlabhq/gitlabhq/issues/6867
Closes https://github.com/gitlabhq/gitlabhq/issues/9194
Sean McGivern