clear rolled back versions from associated model
add test for after_rollback
use begin/rescue/end in block
add test_after_commit gem
Fix spec for PaperTrail::Model::ClassMethods#after_rollback
Merge branch 'pr#440_clear_after_rollback'; closes #440
Code cleanup on PaperTrail::Model::InstanceMethods
Merge branch 'master' of https://github.com/airblade/paper_trail into merge-with-lyfeyaj

Conflicts:
	lib/paper_trail/has_paper_trail.rb