fix(parse): default to angular preset for empty parserOpts (conventional-changelog#265)

Closes conventional-changelog#262

Author: marionebl

@commitlint/parse/src/index.js

@@ -4,7 +4,7 @@ import defaultChangelogOpts from 'conventional-changelog-angular';
 export default parse;
 
 async function parse(message, parser = sync, parserOpts) {
-	if (!parserOpts) {
+	if (!parserOpts || Object.keys(parserOpts || {}).length === 0) {
 		const changelogOpts = await defaultChangelogOpts;
 		parserOpts = changelogOpts.parserOpts;
 	}

@commitlint/parse/src/index.test.js

@@ -105,6 +105,13 @@ test('supports scopes with /', async t => {
 	t.is(actual.subject, 'subject');
 });
 
+test('supports scopes with / and empty parserOpts', async t => {
+	const message = 'type(some/scope): subject';
+	const actual = await parse(message, undefined, {});
+	t.is(actual.scope, 'some/scope');
+	t.is(actual.subject, 'subject');
+});
+
 test('ignores comments', async t => {
 	const message = 'type(some/scope): subject\n# some comment';
 	const changelogOpts = await importFrom(