api#run should return runStatus even when no files are found (#839)

api.js

@@ -105,7 +105,7 @@ Api.prototype._run = function (files, _options) {
 			file: undefined
 		});
 
-		return Promise.resolve([]);
+		return Promise.resolve(runStatus);
 	}
 
 	var cacheEnabled = self.options.cacheEnabled !== false;

test/cli.js

@@ -290,3 +290,11 @@ test('handles NODE_PATH', function (t) {
 		t.end();
 	});
 });
+
+test('works when no files are found', function (t) {
+	execCli('!*', function (err, stdout, stderr) {
+		t.is(err.code, 1);
+		t.match(stderr, 'Couldn\'t find any files to test');
+		t.end();
+	});
+});