Docs: _.reduceRight's Memo is optional
Docs: _.reduceRight's Memo is optional

https://github.com/jashkenas/underscore/blob/master/test/collections.js#L211-L212

documentcloud/underscore,jashkenas/underscore,rlugojr/underscore,jashkenas/underscore,documentcloud/underscore,rlugojr/underscore