test(formly-form): Add test for attribute version of formly-form

Some people prefer to specify directives as attributes only. This adds a test to verify this is
possible. This is a skipped test because I'm going to use it for a first-timers-only issue.

tests for #450

Author: Kent C. Dodds

src/directives/formly-form.test.js

@@ -21,6 +21,14 @@ describe('formly-form', () => {
     scope.fields = [];
   }));
 
+  it.skip(`should be possible to use it as an attribute directive`, () => {
+    const el = compileAndDigest(`
+      <div formly-form model="model" fields="fields" form="theForm"></formly-form>
+    `);
+    expect(el.length).to.equal(1);
+    expect(el.prop('nodeName').toLowerCase()).to.equal('ng-form');
+  });
+
   it('should use ng-form as the default root tag', () => {
     const el = compileAndDigest(`
       <formly-form model="model" fields="fields" form="theForm"></formly-form>