feat: add --resursive and --ignore options (#24)

`--resursive`: Create/update index files recursively. Halts on any unsafe "index.js" files.

`--ignore-unsafe`: Ignores unsafe "index.js" files instead of halting.

src/utilities/readDirectory.js

@@ -37,10 +37,12 @@ const removeDuplicates = (files) => {
   });
 };
 
-export default (directoryPath) => {
+export default (directoryPath, options = {}) => {
   let children;
 
-  validateTargetDirectory(directoryPath);
+  if (!validateTargetDirectory(directoryPath, {silent: options.silent})) {
+    return false;
+  }
 
   children = fs.readdirSync(directoryPath);