Create lockdown test for tag cloud

The tag cloud appears to have 100% code coverage, but it turns out that
there are no assertions regarding this part of the code, it just runs
without raising any exceptions.

Run the lockdown test with `bundle exec rake test:lockdown`.

The lockdown test is an `approval` test, meaning that whatever you
previously approved is considered the correct result.

The first time you run the test there is no previously approved result,
so the test will fail.

To make it pass copy the `.lockdown/received.html` file to
`.lockdown/approved.html`. By doing this you _approve_ the current
output as being correct.

If you run `bundle exec rake test:lockdown` again, the test should pass.
Instance TagCloud and test passing
Move logic to TagCloud
Refactor and remove duplication to sql query string
Get rid of 90days
Using the object at view
Remove duplication in partial
Refactoring TagCloud and remove compute
Clear some logic from the view