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.
- Gemfile switch to mysql2, require factory_girl and selenium
iteration 2
- moved all instance variable assignments to tag_cloud
- clean variables
- moved sql to private method
- move sql to private method
- cleanup sql queries
- pass cut_off to tag_clound and unify methods
- remove instance variables and use TagClound object instead in views
- cleanup _tags template
- cleanup local methods
- move couple more instance variables to methods
- move font size calculation to helper method
Merge branch 'i10'

Conflicts:
	Gemfile.lock