dflags

A header-only replacement for ```gflags```.
Fixed. This was two-fold:

1. Fixed to use ```std::string``` and ```.data()```, had to use ```const_cast<>``` and feel bad that now, Standard-wise, the new, injected, ```argv```-s are not mutable
2. Realized that I can use the old, original, ```argv```-s and just rearrange them. Problem solved!