def add_column(column_name, definition)
      attributes = column_attributes(column_name, definition)
      migration.add_column(*attributes)
    end
def add_column(column_name, definition)
      attributes = column_attributes(column_name, definition)
      migration.add_column(*attributes)
    end
Constructor

 @param migration [ActiveRecord::Migtration]
 @param table_name [String, Symbol]
 Adds the specified column through ActiveRecord

 @param column_name [String, Symbol]
 @param definition [String, Symbol]