Diff3 merge is broken

```
std::string base_code_ = "0";
std::string left_code_ = "100";
std::string right_code_ = "200";

dtl::Diff3<char, std::string> diff3(base_code_, left_code_, right_code_);
diff3.compose();
if (!diff3.merge())
{
    std::cout << "Conflict" << std::endl;
}
else
{
    std::string merged = diff3.getMergedSequence(); // 20 here
}
```
I expect conflict