Do not pass :param_name option in paginate method

Do it in Tag class so we don't have to give it on the helper method.
Do not generate unused records in specs for DataMapper

It takes a lot of time executing specs for DataMapper. This is because we generate 100 user records and 50 project records for the first user. However, that projects data is actually not used in most of the specs. So do not create them if unneeded and do it only for specs that really need them.
reduce number of test Users and Projects

We did the same on 480b78aa4626b82254b6bef356c5869dffecb557, but do we really need 100 records for these specs?