http_build_query() without url encoding

According to [mloughran/signature](https://github.com/mloughran/signature) and [siuying/IGSignature](https://github.com/siuying/IGSignature)

The `parameterString` shouldn't be URL encoded

1. https://github.com/mloughran/signature/blob/master/lib/signature/query_encoder.rb#L16
2. https://github.com/siuying/IGSignature/blob/master/IGSignature/Signature/IGQueryEncoder.m#L13