Adding Full Support to Test Against Multiple DB engines.
Accomplished by swapping out database.yml files for the dummy rails instance with en engine specific one.
On Teardown Restore schema to previous state.
Don't hard code id's in testing...
Postgres return a time as Class Time  not ActiveSupport::Timezone.
(Also another static ID)
Fixing Postgres failing spec.
Changing the test to not use the unsorted with with_item_keys call.
When Cleaning Versions ensure they are in the correct order.
use assert_nil vs .nil? (fix for jruby?)
adding testing papertrail section to Readme [skip ci]
Tests to cover changes from cb46e87; Cleaner module should group versions by PaperTrail.timestamp_field
Merge branch 'test-pg-mysql'

Add support for running the test suite with PostgreSQL and MySQL.
Run the test suite with PostgreSQL and MySQL in addition to SQLite when running on Travis.
Update CHANGELOG [ci skip]
Fallback in user_for_paper_trail to accept current_user returning a string
close #346; cleanup code for 'user_for_paper_trail' default methods, add automated test coverage for various return values
Add warning messages to test helpers for the 'prepare' rake task to avoid confusion [ci skip]
Skip current_user test in Ruby18 due to pesky :id method
Use Rake v10.1 for development because v10.2 requires Ruby19 or higher
fix PaperTrail::Rails::Controller.included method

remove "if" condition and make loading of Rails code conditional.

this bombed if the controller wasn't ActionController::Base and the rails-api gem wasn't included.
Cleanup and organize paper_trail.rb a bit; update CHANGELOG
Separate articles with bullet points on README [ci skip]
Typo fix [ci skip]