Specifying number of runs/iterations at runtime

[aleks-f]

The only way I was able to do it is by hacking and removing const here: https://github.com/nickbruun/hayai/blob/9bdca1c693e950ab2cb17c4ef885792c3c530234/src/hayai_benchmarker.hpp#L287 Otherwise, those numbers are set at startup time and can't be changed later. Or am I missing something?