Made compatible with rails 4 and 4.1

removed attr_accessible

changed key value pair in default rails format
eg. :null => false ---changed_to---> null: false

@base.schema_cache.columns now always need table_name as argument
so changed changed @base.schema_cache.columns[@table_name] to
@base.schema_cache.columns(@table_name)

to_money method is deprecated in latest money gem. used Money.new
instead of to_money

used remove_column to delete an column for database migration