Reduce lodash deps

[wkirby]

Partially addresses #5. We lose a lot of great functionality by abandoning lodash or underscore entirely, but this will at least let us reduce our footprint to just the modules we actually use.

In each all the cases here, the lodash version is at least as fast as the native es6 implementation, so we're not sacrificing performance.

Possible future enhancements include a small refactor to use only components in lodash-core to allow the end user to swap out underscore for lodash with their build tool

[ncallaway]

Looks good. Why is snyk unhappy?

[coveralls]

Coverage remained the same at 100.0% when pulling adfb7f9 on reduce-lodash-deps into fa57e03 on master.