Move C++ files into submodules to make the repo show up as Go project

[jhvst]

To make the project index better in terms of Go, I'd suggest you to create a submodule for both include and handlers folder. You can then delete the tag folder as well. Then the project's main language will then be Go rather than C++.

I tested the changes on my forked project and it seems to work well. Although, as I know little C++ I'd rather have you host the submodules for your own project, so therefore I've not linked a pull request on this issue.