Moved modules into lib folder

no issue

- This fixes a problem where files are skiped form the @tryghost/members-csv package
- Also this follows the file structure convention with other packages

ghost/members-csv/test/parse.test.js

@@ -1,6 +1,6 @@
 const should = require('should');
 const path = require('path');
-const {readCSV} = require('../parse');
+const {readCSV} = require('../lib/parse');
 const csvPath = path.join(__dirname, '/fixtures/');
 
 describe('read csv', function () {