Use lodash modules

This release moves to a modular lodash structure. This should improve load times with module loaders when requiring the join implementations directly. If you require the base module of this library, it will use the full lodash module because it re-exports every join function as mixins.

If you wish to use you're own lodash custom build, it can be generated with:

lodash modern include=flatten,every,filter,groupBy,indexBy,map,reduce,reduceRight,some,sortBy,isUndefined,assign,has,values