Import less Lodash

This module imports the entirety of Lodash which is very large. This results in large bundle sizes for anyone consuming this module. 

This PR imports only the merge function from Lodash.

src/index.js

@@ -1,5 +1,5 @@
 const { resolve } = require('path')
-const { merge } = require('lodash')
+const merge = require('lodash/merge')
 
 export default async function module (moduleOptions) {
   // Apply defaults