only require percentage for percentage discount
added tax option for cart rule
Merge pull request #3 from hiousi/patch-1

[*] MO : only require percentage for percentage discount
// norm
Merge pull request #4 from hiousi/feat_tax

[*] MO : add tax option for discount
// follow up 6029f6334de81c1b2031ecbd2e5490208dce576b add ugrade for configuration key
// Version updated to v1.6.1