Document how to migrate YAML data to JSON
Document how to migrate YAML data to JSON

https://github.com/airblade/paper_trail/pull/662#issuecomment-161348466
airblade/paper_trail,theRealNG/paper_trail,jnstq/paper_trail,theRealNG/paper_trail,jnstq/paper_trail,ifeelgoods/paper_trail,devonestes/paper_trail,airblade/paper_trail,ifeelgoods/paper_trail