Optimize Peeling Machine

[reedacartwright]

Currently the peeling machine is a vector of pointers to functions which gets called with arguments.

for(std::size_t i = 0; i < peeling_functions_.size(); ++i) {
     (*peeling_functions_[i])(work, family_members_[i], mat);
}

We should evaluate whether this is the most efficient strategy. Options include

• Vector of function pointers (current configuration)
• Vector of std::function objects to type erase the underlying function/functor/etc (more flexible option)
• Vector of functor objects with virtual operator()() and family_members_[i] stored internally
• Storing mat[i] instead of family members, but this would require a different peeling machine foreach mat we want to use.

Our current option should be the fastest, if we were not passing variables to it. However, it might be faster to wrap some of the options inside functors with virtual operators or type erasure.