Use clang format

[CharlesGueunet]

I would like to address the issue #9 by myself, however indentation in the code is really hard to understand (mixed tab and spaces). Would it be possible to use a clang-format (or any other tool) to make the code consistent ? I don't really care about which rule to use and I don't feel it is my role to decide it but I can use mine and make a PR if you want.

Charles