ActiveRecord::Migrator.proper_table_name has been removed from Rails

Refer https://github.com/rails/rails/commit/6da0072

It has not supported `table_name_prefix` and `table_name_suffix` yet.
Merge pull request #481 from yahonda/rails42_proper_table_name_method_removed

ActiveRecord::Migrator.proper_table_name has been removed from Rails