Introduce non_auditable_columns lazy method.
Merge remote-tracking branch 'hron_audited/lazy-non-audited-columns-for-3.0.0'

# By Aleksei Gusev
# Via Aleksei Gusev
* hron_audited/lazy-non-audited-columns-for-3.0.0:
  Introduce non_auditable_columns lazy method.

Conflicts:
	lib/audited/auditor.rb