Ignore node_modules when running prettier from CLI (#1683)

* Ignore node_modules by default

* Add integration test suite for --with-node-modules CLI arg

* Refactor tests to snapshots

* Disable eslint for purposely faulty files

* Fix node 4

* Fix prettier

* Gitignore only top-level node_modules

tests_integration/cli/with-node-modules/node_modules/node-module.js

@@ -0,0 +1,2 @@
+/* eslint-disable */
+'use strict';

tests_integration/cli/with-node-modules/not_node_modules/file.js

@@ -0,0 +1,2 @@
+/* eslint-disable */
+'use strict';

tests_integration/cli/with-node-modules/regular-module.js

@@ -0,0 +1,2 @@
+/* eslint-disable */
+'use strict';