v2.1.6

Feature:

1. Add new http client implementation, see netutil/http_client.go
2. Add condition package for conditional judgment, see condition/condition.go
3. Add function EncodeByte and DecodeByte, see convertor/convertor.go
4. Add function IsZeroValue, see validator/validator.go

Fix:

1. Fix hash algorithm bug in datastructure/HashMap.go