Merge pull request #1 from rshallit/next

fix version.valid_item_type? method
fix validators namespace
allow :object_changes to be mass-assigned...

... per original paper_trail gem versions model
line got dropped
prefer generic ruby-env management over rvm
preliminary validators for csv and excel
Merge branch 'hotfix/validator_to_engine' into next
enginize validation
improved error reporting
refactored CSV importer
Merge pull request #2 from rshallit/next

Refactor class name validations
add activerecord-import
importing spec
fix csv importing