wrong length for IRemoteSchemaDocumentProvider

[niukuo]

#include <rapidjson/schema.h>
#include <rapidjson/document.h>
#include <string>
#include <iostream>

namespace rapidjson {

class MyRemoteSchemaDocumentProvider : public IRemoteSchemaDocumentProvider {
public:
    virtual const SchemaDocument* GetRemoteDocument(const char* uri, SizeType length) {
        std::string str(uri, length);
        std::cout << str << std::endl;
        return NULL;
    }
};

}

int main()
{
    using namespace rapidjson;
    Document doc;
    SetValueByPointer(doc, "/$ref", "schema_prefix#/path");
    MyRemoteSchemaDocumentProvider provider;
    SchemaDocument schema(doc, &provider);
}

it outputs schema_prefi
but it should outputs schema_prefix

I have already created a pull request #723
hope to fix and release