extension guide and example (#623)

* extension guide and example

* code and guide fixes

* update dependencies

projects/my-extension/src/lib/my-extension.component.spec.ts

@@ -0,0 +1,25 @@
+import { async, ComponentFixture, TestBed } from '@angular/core/testing';
+
+import { MyExtensionComponent } from './my-extension.component';
+
+describe('MyExtensionComponent', () => {
+  let component: MyExtensionComponent;
+  let fixture: ComponentFixture<MyExtensionComponent>;
+
+  beforeEach(async(() => {
+    TestBed.configureTestingModule({
+      declarations: [ MyExtensionComponent ]
+    })
+    .compileComponents();
+  }));
+
+  beforeEach(() => {
+    fixture = TestBed.createComponent(MyExtensionComponent);
+    component = fixture.componentInstance;
+    fixture.detectChanges();
+  });
+
+  it('should create', () => {
+    expect(component).toBeTruthy();
+  });
+});