fix(errors): default options so transform works without a second argument

errors.js

@@ -11,7 +11,8 @@ const { LEVEL, MESSAGE } = require('triple-beam');
  *
  * Optionally, the Error's `stack` and/or `cause` properties can also be appended to the `info` object.
  */
-module.exports = format((einfo, { stack, cause }) => {
+module.exports = format((einfo, opts = {}) => {
+  const { stack, cause } = opts;
   if (einfo instanceof Error) {
     const info = Object.assign({}, einfo, {
       level: einfo.level,

test/errors.test.js

@@ -143,3 +143,14 @@ describe('errors()(Error)', () => {
     { immutable: false }
   ));
 });
+
+describe('errors().transform called without options', () => {
+  it('does not throw when transform is called with a single argument', () => {
+    const errorsFormat = errors({ stack: true });
+    const transformErr = new Error('Oh no!');
+    const info = errorsFormat.transform(transformErr);
+    assume(info).is.an('object');
+    assume(info.message).equals(transformErr.message);
+    assume(info[MESSAGE]).equals(transformErr.message);
+  });
+});