Higher-order procedures

[MSE99]

I know that the goal of this project is to provide a clean and efficient minimal API but i think having for example a some high order procedures like Filter will help improve usage and dx.

[benbjohnson]

I'm open to a proposal for higher-level functions (e.g. Filter, Map(), etc). I don't commit a lot of time on this repo so I don't have the bandwidth to implement it but I'm open to other folks implementing something.

[MSE99]

Should we pass other information (other than the current item) about the list to Filter predicate?

[laher]

@MSE99 I have prototyped some HOFs here: #37 ? Does they seem like what you were hoping for?