Avoid scope error in tests (Mongoid 4)

[johnnyshields]

Mongoid 4 throws the following errors when running specs. This PR only modifies the specs/non-lib files to fix it. Verified it works on Mongoid 3 as well.

• Issues with loading Mongoid Paranoia gem (have also changed to using official release version of Mongoid Paranoia)

• Scopes must be procs on Mongoid 4

  /lib/mongoid/scopable.rb:306:in `check_scope_validity':  (Mongoid::Errors::InvalidScope)
  Problem:
    Defining a scope of value #<Mongoid::Slug::Criteria:0x4195c20> on Page is not allowed.
  Summary:
   Scopes in Mongoid must be procs that wrap criteria objects.
  Resolution:
   Change the scope to be a proc wrapped critera.
  

[digitalplaywright]

Thanks! The tests are now green again. I fixed the remaining issue after this.