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.
Extract TagCloud object.
Move all to TagCloud model
Rename variables
Extract sql in method.
Move second sql into method.
Remove duplication in sql statement
Use two objects
Use TagCloud objects in view
Remove duplication in view
Move tags calculation to method
Clean up TagCloud
Clean up view
Merge branch 'iteration9'

Conflicts:
	lib/tasks/wip.rake